The Druid Handbook

[Mooncrow]

Much thanks to Blade2718 for the original handbook, and allowing it to be moved over and modified.

The Druid Handbook

Because Druids and Druid derivatives are so popular and powerful, I think that BrilliantGameologists should have its own Druid Handbook.  I had some time on my hands so I figured "Why not me?"  I must confess that I am no expert on the topic, that I stand on the shoulders of giants, and that this is primarily a recompilation effort.  Much of the material presented will be derived from sources from the Wizards of the Coast d20 Character Optimization forums, including but not limited to:
Dictum Mortuum's "CO Project: The Quickstart Druid
A Man In Black's "Druid Handbook revived"
Dead Weasel's "Alternative Class Features III"
Lord_of_Rivendell's "Revisiting Spells for the Optimized Druid"

This should not be considered an authoritative guide.  I welcome any collaboration and polite feedback.  Thanks for reading!

(Feedback and suggestions can go in this thread)

Table of Contents

1. Introduction
2. Class Features and Alternatives
3. Skills, Skill Tricks, and Feats
4. Spellcasting
5. Animal Companion
6. Wild Shape
7. Equipment
8. Controversy and Miscellany
9. Appendices

Color Code:
Blue = great option, highly recommended.
Green = a good option, though either less powerful or more limited than a blue
Black = an average option, not terrible, but either of very limited use or very weak.
Red = a bad option, do not take.

[Mooncrow]

Druids are guardians of nature, able to call down the wrath of the natural world, befriend wild animals and take on their aspects, yadda yadda yadda.  You didn't come for a flowery description of druids, though given time I could come up with one.  We're here for the crunchy bits that matter to many players.

Attribute Distribution

• Strength: Not a priority, unless you are a melee combatant early in your career and you need the extra damage.
• Dexterity: Not a priority, unless you are a melee combatant early in your career and you need the extra AC
• Constitution:  This is a very close second to Wisdom for your most important stat, as it determines your HP in both native and alternate forms.  It also modifies your Concentration skill.
• Intelligence:  Not a priority, but good to have.  This class has 4+Int skill points, and there aren't too many skills that you would need to keep at maximum, anyway.
• Wisdom:  This your first priority stat, as it determines bonus spells, spell DCs, and highest spell level known.  It also modifies several important skills.
• Charisma:  Not a priority, unless your character concept requires a strong social ability.  It also modifies your Wild Empathy ability.

Party Role(s)
The Druid's variety of class abilities allow for an equally diverse number of roles in the party.

• Primary Melee: Medium armor, shield proficiency, and several good weapons make you a good candidate for front line work.  Greater emphasis on physical stats will become necessary at lower levels, while animal forms will predominate at the later levels.  You also have a number of spells that enhance your damage or boost your defense.
          Sample Builds:
• Primary Ranged: Your only projectile weapon is a sling, which doesn't allow for iterative attacks.  Elves and Outsiders have the advantage with natural access to martial weapons.  You have several spells, though, that can be used at range such as produce flame and fire seeds.
          Sample Builds: Druidic Avenger 12
• Primary Skillmonkey/Stealth Expert: Your high Wisdom and access to Listen and Spot as class skills also make you a good scout.  Wild shape further enhances this, allowing you to take the form of innocuous wildlife like songbirds.  Access to Diplomacy also lets you be the party's face.
          Sample Builds:
• Primary Healer: Though not as obvious a choice as the Cleric, you still have access to healing spells, can use healing wands, and can summon unicorns to heal for you.
          Sample Builds:
• Primary Buffer: Your best buffs apply to your animal friends, but everyone benefits from barkskin.
          Sample Builds:
• Primary Caster: Summoning is a natural strength for you, and your have a variety of damage-dealing and control spells to choose from.
          Sample Builds:

Racial Selection
I won't waste time with every racial option, just highlight some interesting options.  Most unlisted races either clearly suboptimal or simply mediocre.

• Human: With their racial feat and racial bonus skill point, Humans are the perennial favorite.
• Strongheart Halfling^FRCS: Small size and a free racial feat.
• Ghostwise Halfling^FRCS: Trade the standard +1 to saves for a supernatural form of telepathy to make it much easier for you to communicate with your allies while wildshaped.
• Anthropomorphic Bat^SS: Huge bonus to Wisdom and blindsense are an attractive package.
• Dragonborn^RotD: Good for a Constitution bump.  The magic really happens when you start creating Dragonborn from obscure races, like...
• Buomman^Pla: Bonus to Wisdom, but a vow of silence.  Note that the racial vow of silence buommans have is waived should you opt to undergo dragonborn transformation.  Like plastic surgery, but better, because it also gives you a Constitution bonus.
• Half-orc: There are great half-orc druid substitution levels, so this race bears mentioning.  Unearthed Arcana has a Desert Half-Orc that trades Strength for Constitution, and doesn't penalize Cha, making it a superior choice if the variant race is allowed in your game.
• Shifters^ECS/RoE/MM3: At low levels, any Shifter with a natural attack shifting ability can be using the druid spells to enhance their natural attacks. Later on, your shifting bonus will stack with Wild Shape (Shifting is a supernatural ability, so you keep it in Wild Shape), which not only means stat bonuses, but also gives extra AC, new move types, or even possibly extra attacks. Dreamsight Shifters (RoE), in particular, give +2 Wis and Speak With Animals while shifting, but all of the Shifter traits give untyped bonuses to stats that still work while shifting, so any of them can work quite nicely. Plus, it allows you to take, say, Improved Natural Attack (claws) or INA (bite) even if your GM won't usually allow you to take those for forms you can only take with Wild Shape. Shifters can also take Moonspeaker (RoE), one of the few good druid PrCs.  Beasthide, Dreamsight, Longtooth, and Razorclaw Shifter traits are good for druids, because those benefits stack nicely onto whatever animal form you might be using.  Taking Shifter also allows you to use the Shifter sub levels. The first Shifter sub level costs you your Animal Companion, but replaces it with a Beast Spirit that can buff you, buff your summons, cuts your summons to a standard action, and can eventually cast quickened spells for you. (All the bonuses make this an absolutely awesome choice for any sort of druid.) Most druids will want to avoid the fifth sub level, unless you're planning to specialize heavily in shifting.
• Kalashtar^ECS: Their mindlink ability (you definitely want to use the XPH version of mindlink for a much longer duration) allows them to communicate even while Wild Shaping, and they can take psionic feats to boot, like Speed of Thought.
• Jermaline^MM2: Tiny Fey with penalties to Str, Cha, and Con are offset by LA +0 with massive Wis and dexterity bonuses.

[Mooncrow]

Standard Class Features
"I am a Druid, I have special abilities that are more powerful than your entire class!"  'Nuff said.

• Spells: Spellcasting is one corner of the trifecta that is Druid.  The fact that it will receive its own section in the guide should attest to its awesomeness.
• Bonus Languages: I only mention this because Druid is the only class that adds an automatic language (not to be confused with bonus languages), Druidic.  This language is usually the major stumbling block for players wishing to enter the Fochluchan Lyricist prestige class.
• Animal Companion (Ex): At first glance, you'd wonder what makes your animal companion so awesome, but you realize how very useful an obedient animal can be for you.  Especially after you buff it into an engine of destruction.  This will also get its own section, review the different companions you can get.
• Nature Sense (Ex): Sort of like the ugly sweater your grandmother gives you: love her, hate the gift.
• Wild Empathy (Ex): Animal Diplomacy.  But it's a lot harder to get an animal to be helpful, because the check is harder to modify.
• Woodland Stride (Ex): While it's not exactly a medal-winner in its own right, it helps you if you have to be the scout.
• Trackless Step (Ex): Nice if you're being followed, but...that's about it.
• Resist Nature’s Lure (Ex): If you're facing a lot of Fey, it's okay, but otherwise it's just a step along the path toward...
• Wild Shape (Su): This is the reason you picked Druid.  It's own section is later, but suffice it to say that this is where the Druid's Real Ultimate Power comes from.
• Venom Immunity (Ex): At least we won't have to worry about assassins...
• A Thousand Faces (Su): Free disguising is good, but true seeing has been available for a while.
• Timeless Body (Ex): Say goodbye to aging penalties!  If you're starting at this level, feel free to age yourself to venerable for the extra untyped +3 to mental stats.

Alternate Class Features
Many of these abilities are situational, so I won't rank any of them.  Decide which ones you like best for yourself.

Alters Armor/Weapon Proficiencies

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Deadly Hunter (UA, p 58): Gain bonus to AC when unarmored and fast movement (as monk). Gain favored enemy, track, and swift tracker as a ranger. Lose armor and shield proficiency and wild shape.

Alters Spellcasting

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Druidic Avenger (UA, p 51): No Animal Companion or Spontaneous Casting, penalty to Wild Empathy. Gain Fast Movement and Rage.
Fangshields Druid 4 (CoV, p 40): Must be non-humanoid.  Spontaneous Curing.  Replaces Resist Nature's Lure.
Halfling Druid 1 (RotW, p 157): Add Climb, Hide, Jump, and Move Silently to skill list.  6 skills points per level.  Spontaneous Casting (Special list of spontaneous spells), Enhanced Link (bonus to ride animal companion)
Half-Orc Druid 6 (RoD, 159): d10 hitdice, Add Intimidate as class skill.  6th level: Augmented Nature's Allies (+4 Str/Con on SNA's), lose one wildshape/day.
Goliath Druid 1 (RoS, p 151):  Elemental Bond (better earth summons, can't summon other elements)
Spontaneous Affliction (EoE, p 21): lose ability to spontaneous SNA, gain ability to sicken humanoids.
Spontaneous Rejuvenation (PHB2, p 39): Lose spontaneous SNA spells. Gain the ability to sacrifice spells to give allies fast healing.

Alters Animal Companion

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Aquatic Druid (Storm, p 50): Choose an aquatic animal companion.
Druidic Avenger (UA, p 51): No Animal Companion or Spontaneous Casting, penalty to Wild Empathy. Gain Fast Movement and Rage.
Elemental Companion (CM, p 33): Gain an Elemental as a companion instead of an animal.
Halfling Druid 1 (RotW, p 157): Add Climb, Hide, Jump, and Move Silently to skill list.  6 skills points per level.  Spontaneous Casting (Special list of spontaneous spells), Enhanced Link (bonus to ride animal companion)
Half-Orc Druid 1 (RoD, 159): d10 hitdice, Add Intimidate as class skill. Animal Companion gains Toughness.
Goliath Druid 6 (RoS, p 151): Earth Companion (animal companion gains earth-type and some stat changes)
Phynxkin Companion (DrM, p 13): Gain a phynxkin instead of your normal animal companion.
Plant Companion (DragMag 357): Gain a plant companion instead of an animal.
Shapeshifter (PHB2, p 39): Lose animal companion and wildshape. Gain the ability to change into several forms, with set bonuses, at will.
Shifter Druid 1 (RoE, p 126): Add Balance, Climb, and Jump to class skills.  Beast Spirit (grants powers and abilities as level increase). Replaces animal companion.
Urban Companion (City, web): Instead of a normal animal companion, instead gain something similar to a familiar.

Alters Nature Sense

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Urban Sense (City, web): Lose nature's sense, gain a +2 bonus to sense motive and knowledge: local checks.

Alters Wild Empathy

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Druidic Avenger (UA, p 51): No Animal Companion or Spontaneous Casting, penalty to Wild Empathy. Gain Fast Movement and Rage.
Half-Orc Druid 4 (RoD, 159): d10 hitdice, Add Intimidate as class skill. Bully Animal (use Str instead of Cha for wild empathy), lose resist nature's lure.
Root Walker (DS, p 9): Lose Woodland Stride, Resist Nature's Lure, and Wild Empathy. Gain Wild Empathy towards vermin; move over earth, stone, and rock debris; and +4 bonus on saving throws against spell like abilities of abberations.
Voice of the City (City, web): Lose wild empathy to gain the ability to communicate with people who speak languages you do not know.

Alters Woodland Stride

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Crowd-Walker (City, web): Exchange woodland stride for the ability to move in crowds more easily.
Root Walker (DS, p 9): Lose Woodland Stride, Resist Nature's Lure, and Wild Empathy. Gain Wild Empathy towards vermin; move over earth, stone, and rock debris; and +4 bonus on saving throws against spell like abilities of abberations.
Sandskimmer (Sand, p 47): Gain Sandskimmer, lose Woodland Stride.

Alters Trackless Step

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Go to Ground (City, web): Lose trackless step, gain the ability to hide from Urban Tracking.

Alters Resist Nature's Lure

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Fangshields Druid 4 (CoV, p 40): Must be non-humanoid.  Spontaneous Curing.  Replaces Resist Nature's Lure.
Half-Orc Druid 4 (RoD, 159): d10 hitdice, Add Intimidate as class skill. Bully Animal (use Str instead of Cha for wild empathy), lose resist nature's lure
Heat Endurance (Sand, p 47): Gain Heat Endurance, lose resist nature's lure.
Iron Constitution (City, web): Lose Resist Nature's Lure. Gain the Strong Stomach feat, and +2 bonus to saves against disease.
Planar Druid 4 (Pla, p 31): Gain Knowledge: The Planes as a class skill.  Resist Planar Might (+2 bonus to saves to resist spell-like abilities of outsiders).  Lose Resist Nature's Lure.
Root Walker (DS, p 9): Lose Woodland Stride, Resist Nature's Lure, and Wild Empathy. Gain Wild Empathy towards vermin; move over earth, stone, and rock debris; and +4 bonus on saving throws against spell like abilities of abberations.
Shifter Druid 4 (RoE, p 126): Add Balance, Climb, and Jump to class skills. Reckless Nature (+2 initiative checks and reflex saves, -2 to will saves) replaces Resist Nature's Lure

Alters Wild Shape

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City-Shape (City, web): Smaller wild shapes, but gain the ability to change into vermin.
City-Soul (City, web): Lose the ability to wild shape into an elemental, turn into animated objects instead.
Aspect of the Dragon (DrM, p 11): You don't gain wildshape. Instead take on various aspects of dragons.
Drow Druid (DotU, p58): Wildshape into a monstrous spider instead of animals.
Halfling Druid 5 (RotW, p 157): Add Climb, Hide, Jump, and Move Silently to skill list.  6 skills points per level.  Undersized Wildshape (wildshape limited to smaller forms, usable more times per day)
Half-Orc Druid 6 (RoD, 159): d10 hitdice, Add Intimidate as class skill.  Augmented Nature's Allies (+4 Str/Con on SNA's), lose one wildshape/day.
Fangshields Druid 5 (CoV, p 40): Must be non-humanoid.  Wild Shape Hands (form hands while wildshaping)
Fangshields Druid 7 (CoV, p 40): Must be non-humanoid.  Wild Shape (Humanoid), lose 1 use of wild shape.
Goliath Druid 12 (RoS, p 151): Earth Wild Shape (change into an earth elemental instead of plant)
Shapeshifter (PHB2, p 39): Lose animal companion and wildshape. Gain the ability to change into several forms, with set bonuses, at will.
Shifter Druid 5 (RoE, p 126): Add Balance, Climb, and Jump to class skills.  Wild Shifting (can use racial shifting an extra time per day, and add Wisdom bonus to duration. At 8th level claws are treated as one size larger, at 15th level they are treated as two sizes larger. Gain additional uses each time you would gain more uses of wildshape.).  Replaces normal wildshape ability. At 16th level, gain the ability to change into an elemental as normal.
Waste Vermin Wildshape (Sand, p 47): Wildshape into a wasteland vermin, lose 1 wildshape/day.

Alters Venom Immunity

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Planar Druid 9 (Pla, p 31): Gain Knowledge: The Planes as class skill.  Planar Tolerance (become attuned to planes).  Lose Venom Immunity.

Alters Thousand Faces

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Halfling Druid 13 (RotW, p 157): Add Climb, Hide, Jump, and Move Silently to skill list.  6 skills points per level.  Camouflage.  Lose Thousand Faces.
Planar Druid 13 (Pla, p 31): Gain Knowledge: The Planes as class skill.  Counter Summoning (counter summon monster spells).  Lose Thousand Faces.

Wild Reaper Variant^{Dragon 311} - this version changes a lot of things, and it's one of the few upgrades to the base druid chassis.
Alters:
Wild Shape - forms must be carnivorous or omnivorous animals that eat carrion.  No plant or elemental forms.
Spells - A much larger list of spontaneous casting, several of which are very nice.  Spontaneous castings is delayed until 3rd level
Animal Companion - same rules as wild shape
Poison Immunity - traded for disease immunity
Turn Undead - At 12th level, the Wild Reaper gets Turn Undead - qualifying the druid for DMM
A Thousand Faces - traded for a +4 bonus to saving throws against death effects and level drain
Fast healing 1 - gained at 16th level, increases to fast healing 3 at 20th
Ability damage healing 1 - gained at 17th level, increasing to ability damage healing 2 at 20th
Timeless Body is delayed until 19th level

[Mooncrow]

Druid Class Skills

• Concentration: Because you'll probably be casting in melee after you get wild shape, you need to max it out. Even if you use wild shape forms as a defensive form for casting (such as a high AC flying form), it would be a major risk to not max this out.
• Craft: Unless you want to fulfill a certain requirement, don't get this. This skill, however, has some use. To create a bogun with the beget bogun spell, you need to make a craft (basketweaving or weaving) check of 12. If the little critters appeal to you, get 2 ranks in craft (basketweaving or weaving) skill and take 10.
• Diplomacy: With this you can even be the party's face if need be. You can also use it to haggle and get a discount on items.
• Handle Animal: Important due to the synergy with animals and your animal companion. You need a total score of +20 to make the most of this skill, which means that you need to spend ten ranks more or less (assuming you take 10 on its use). Get 5 ranks if you want the synergy bonuses. See The Handle Animal Guide for more information on how to make optimal use of this skill.
• Heal: Not much here. If you feel like it, you can spend 5 ranks and take 10 to use some of the skill's functions.  10 ranks lets you remove exhaustion, nausea, and sickness with healing lorecall.
• Knowledge (Nature): It's your only knowledge, so it would be best to max it.
• Listen: Spend at least 12 ranks in this skill to make use of the listening lorecall spell.
• Profession: You make more money adventuring, anyway.
• Ride: Only useful if you want to use your animal companion as a mount. Still, only a few ranks are needed.
• Spellcraft: It's usually a good idea to max it or at least keep it high. If you are going to play in an epic campaign, you must max it, as you'll need it for epic spellcasting.
• Spot: This usually comes with listen. Spend a few points if you feel like it or your party is in need of a scout.
• Survival: Get 5 ranks for the synergy bonus. You can max it out, it's a skill with druidic feel. You can get the track feat to benefit most from it.

Cross-Class Skills

• Balance: Getting it to 5 ranks will make sure that you won't be flat-footed when you are balancing. Also you'll be able to use balancing lorecall to a greater effect.
• Knowledge: Try to get one rank in each other subdivision of Knowledge.
• Use Magic Device/Use Psionic Device: If you have ranks to spare, invest just one here.
• Autohypnosis: It has wisdom synergy and a synergy bonus from concentration, so you can get it at high levels without investing many ranks. It has cute functions, too.

Skill Tricks
Introduced in Complete Scoundrel, tricks provide little abilities that are usable once per encounter but are not deemed as powerful as a feat.  Each trick has skill prerequisites and requires
two ranks to learn.

• Listen to This: Useful if you are going to be the party's scout.
• Swift Concentration: Druids have enough concentration-duration spells to make this skill trick a good buy.

Feats
Feats are a very limited resource, barring embrace the dark chaos/shun the dark chaos cheese.

• General Druid Feats
         
  • Natural Spell:  This is the reason Druids rock so hard.  You can wild shape into an itty-bitty sparrow and rain Empowered Maximized fire seeds on your opponents.  You can cast produce flame while fighting in melee as a dinosaur.  The potential is limited only by your book collection and imagination.
  • Animal Devotion - some nice powers, especially for melee druids - scaling sacred/profane Str bonus, scaling sacred/profane base speed bonus, or flight.  Usable multiple times a day with the Wild Reaper variant.
  • Initiate of Nature^PGtF: This feat allows you to rebuke animals and plants. You have the ability to control HD per class level, of which no one creature can be more than 1/2HD per class level. Combined with the animal buffing spells you receive, it's a reasonable choice.  Oh, right- it adds briartangle, mold touch, and tree healing to your spell list, too.
  • Ironwood Body^RoE: A must-have for Warforged druids, assuming your DM allows it.
  • Manifest Druid^PGtE: A flavor feat, with a handful of nice bennies (although the Sudden Empower for a first-level arcane spell is just weird).
  • Companion Spellbond^PHBII: extends the range of your Share Spell ability from 5' to 30'.  Very useful for those who don't use the companion as a mount.
  • Natural Bond^CAdv: Helps out multiclass Druids with their animal companions. May offset the penalty for stronger-than-standard Animal Companions (ask your GM), which makes it not just good, but borderline cheese.  But hey, whatever he's allowing...
• Summoning Related Feats
         
  • Augment Summoning: +4 bonus to strength and dexterity is a good bonus, but the problem is that it requires a useless feat, spell focus (conjuration). Luckily for us, there are ways around that (like initiate of malar or the 7th half-orc substitution level).  Still, it's worth taking no matter what if you're going to be doing summoning.
  • Greenbound Summoning^LEoF: At low levels, this is insanely powerful, enough that you'll get dirty looks at your table.  Once you hit 9th level and get animal growth, its relative power drops quite a bit though. 
  • Rashemi Elemental Summoning^UE: Lets you turn your air elemental summons into orglashes with 3/day cone of cold and earth elemental summons into thomils that engulf.  This is very nice way to keep your summons relevant at higher levels when the animal summons begin to fall off.
  • Ashbound^ECS: Doubles the duration of summons and gives them a luck bonus to attack.
  • Beckon the Frozen^Frost: +1d6 cold damage on all your summoned critters' attacks. Pretty weak compared to the other summoning feats, but ok if you're looking to squeeze out every last drop of damage from your summons.  Not available if you bypass the Spell Focus (Conjuration) prereq of Augment Summoning, as the Spell Focus is specifically called out in this feat's prereqs.
  • Imbued Summoning^PHB2: Buy a Summoner's Totem^MiC instead. 
  • Initiate of Malar^PGtF: Gives animal-only Augment Summoning for free, and also gives some pretty lame extra spells. You have to worship Malar, though, which conflicts mechanically with Exalted feats (seeing as Malar is evil and all) and thematically with Rashemi Elemental Summoning. (The Hathrans do not often teach their secrets to followers of Malar.)
• Wild Shape Related Feats
         
  • Dragon Wild Shape^Drac: Another great feat, a must have at level 12. You get all supernatural and extraordinary abilities of the dragon you wild shape into. Note that dragons normally speak and can cast spells, so you probably don't need natural spell, but a consensus is needed here.
  • Bestial Charge^CC - great for those druids who love melee combat; get pounce on all your forms, or a +3 attack bonus on forms that already have pounce, and the ability to change direction during a charge.
  • Multiattack^MM: Many forms have secondary natural attacks. This makes them more accurate. Some GMs may disallow this because you don't always have the natural attacks, however. (This is assuming you're not a Shifter or something.) Probably only worth taking in a core-only game, though.
  • Improved Natural Attack^MM: Extra damage on a single type of natural attack. INA (bite) or INA (claws) is very handy, and counts as a Shifter feat if you're a Shifter.
  • Exalted Wild Shape^BoED:  Free, if minor, bonuses while Wild Shaping, as the Celestial template can be applied to any animal form you can usually take. It also makes blink dog and Unicorn (as well as some other, mostly useless) forms available, all Ex and Su abilities included. You may be able to talk your GM into including Scent, Blindsense/Blindsight, and other Ex abilities of animal forms you can take. (The feat does say you get the Ex and Su abilities of forms you can take with this feat.) If this is allowed, this feat is much more useful. Note that this feat doesn't benefit your Plant, Elemental, or any other type of form you can take; just animals or the limited list of Magical Beasts.
  • Frozen Wild Shape^Frost: This feat should just be renamed Twelve-Headed Cryohydra Wild Shape.
  • Assume Supernatural Ability^SS: Totally broken feat.  If you're a GM, don't say I didn't warn you. If you're a player, well, welcome to flavor town.
• Spellcasting Feats
         
  • Extend Spell: A good choice to extend buffs.
  • Energy Substitution^CA and Energy Affinity^Mini: If you do a lot of blasting, you may want this. I'd recommend cold or acid, since most of the best and most popular druid blasts are fire or electric. If your GM is silly enough to allow Energy Sub (Sonic) (from Tome and Blood), by all means take advantage.
  • Empower Spell: Handy for druids who do a lot of blasting, but only druids who do a lot of blasting. Definitely choose this over Maximize Spell or Energy Admixture. (Leave those to Incantatrices and Blastificers.)
  • Ocular Spell^LoM: Turns touch spells into rays, and lets you cast two spells as a full action. Druids can't cheese it out quite as much as some classes, but this broken feat benefits them greatly.
  • Persistant Spell^CA: Reeeeeally expensive, but as usual it's an exceedingly powerful feat even for casters who can't abuse Divine Metamagic. Apparently Help Desk thinks it can work on touch spells; that's probably not a good idea to allow as a DM, but a ridiculously powerful option if it's allowed to you as a player.
  • Quicken Spell: A staple of high-level prepared casters. Quickened buffs are always a good choice.
  • Sculpt Spell^CA: Sculpt Spell is always handy for blasters and controllers, and Druids can do a bit of both. This can be handy to use on limited or weird areas of effect, to make them more useful.
  • Gatekeeper Initiate^ECS: This druid-only Initiate feat gives you Knowledge (planes) as a class skill, and gives a ton of great defensive spells, including Protection From Evil, Dimensional Anchor, and Mind Blank. A great pick, especially in high-level parties with no cleric.
  • Greensinger Initiate^ECS: Adds Bluff, Hide, and Perform to your class skill list, and adds a ton of handy enchantments (plus some oddballs) to your spell list.
  • Initiate of Gruumsh^CoR: Not a great Initiate feat, but once a day you can quicken a Cure spell. but the one time it saves a life, you'll be praising Gruumsh all night long.
  • Initiate of Malar^PGtF: Mentioned above, this gives you a handful of mostly-useless spells and free Augment Summoning on all of your animal summons.
  • Initiate of Selune^PGtF: This is one of the weaker Initiate feats, but it gives an improved version of Produce Flame, as well as a shield-typed AC buff, so it's not all bad.
  • Nightbringer Initiate^FoE: Adds the sneaky skills (Hide and Move Silently) to your skill list, and gives you access to Darkness, Deeper Darkness, and a handful of negative energy spells and spells to create or call natives of Mabar. Enervation is the nicest spell of the lot.
  • Warden Initiate^ECS: +2 to AC when in a forest, plus a handful of useful utility spells. Not as good as the other Eberron Initiate feats, but still a good feat.

[Mooncrow]

Druids are full casters, no matter how much you beat things up with your bare paws.  Your ability to escape from danger or create danger for your opponents is, at least, partially dependent on what spells you have available.

0th Level

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Create Water: Never run out of water. Plus, you can make a scrying pool.
Cure Minor Wounds: One point isn't a lot, but this can stabilize a dying ally.
Detect Magic: One of the most powerful and versatile zero-level spells, for any caster.
Guidance: Tell your Rogue to ask for "guidance" prior to every trap he attempts to disarms or UMD roll he has to make (outside of combat). That +1 bonus can be critical.
Light: Remember, you lose darkvision when you Wild Shape, even if your chosen form has it. (Obviously, this doesn't apply to situations where you're getting Ex special qualities of your form, as with Exalted or Dragon Wild Shape.)

1st Level

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Acquatic Escape^CSc: Change into a fish for 1 round/level. Good for sudden escapes or quick responses to getting dumped into water.
Aspect of the Wolf^SpC: This is a fairly handy melee self-buff for early levels (instead of going the wooden club route with Shillelagh). At later levels, you can share it with your Animal Companion to help deal with the practical issues of traveling with a snarling bear the size of a bull elephant.
Babau Slime^SpC: Great for grappling druids, and a general-purpose damage buff for any Wild Shaping Druid.
Beget Bogun^SpC: Creates a small little creature to do your chores.
Camouflage^SpC: +10 to Hide, and it works in any environment.
Endure Elements: A great travelling spell, and especially handy in any game that takes you into harsh environments.
Enrage Animal^SpC: A solid buff for your animal companion, enabling it to rage like a barbarian without the fatigue.
Entangle: A best-in-class battlefield control spell.
Eyes of the Avoral^BoED: Long duration, big Spot bonus.
Faerie Fire: Good for dealing with invisible foes.
Lessor Vigor^SpC: This spell actually outperforms Cure Light Wounds, especially out of combat. Wands of Lesser Vigor are great for healing between fights.
Magic Fang and Silvered Claws^BoED: Decent buff to help your Animal Companion bypass DR. Not very good for anything else.
Obscuring Mist: The next best thing to invisibility, when it comes time to get out of a fight. Cast Mist, walk 5 feet backwards, and run away in a different direction.
Omen of Peril^SpC: Poor man's Augury. Quite possibly the most versatile first-level divination in the game, and doesn't even have a costly component or XP cost, like many similar divinations.
Pass Without Trace: Not for the druid, but to cover the tracks of her companions.
Produce Flame: Fairly powerful attack spell. You'll probably be relying on this to attack until you get Wild Shape, and makes a decent buff (due to the way holding touch spells works) after you get Wild Shape.
Rot of Ages^DrM: lol no sneak attack 4 u. Too bad about the short duration, though.
Shillelagh: It's pronounced "shi-lay-lee." Dramatically increases club/quarterstaff damage (to the point where you'll actually want to wield a club or quarterstaff), and stacks with Spikes and Brambles. Decreases in usefulness after you get Spikes, until you're high enough level to Quicken it.
Spider Hand^BoVD: Best. Scouting. Spell. Ever. Send out a nondescript spider to do all the scouting, with only negligible consequences if it dies? Yeah, I'll take that. It's not even an evil spell.
Thunderhead^SpC: 1d6 damage per round/level unless they make a reflex to negate, and also acts as a tracker against targets who turn invisible
Twilight Luck^BoED: +1 on saves is always handy, especially at higher levels. Just lay off the booze.
Winged Watcher^CSc: Change into a bird for 1 round/level. Good for sudden escapes or quick responses to needing to fly.
Wood Wose^SpC: Unseen Servant, only druidic. It just can't handle doorknobs.

2nd Level

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Acorn of Far Travel^WotC - A nice spell from the "Far Corners of the World" article series that lets you emulate forested terrain to improve spells such as deadfall, creaking cacophony, fey ring, or splinterbolt.  You can also use the acorn as an oak tree for spells like tree stride or transport via plants.
Align Fang^SpC: Handy for DR problems.
Animalistic Power^PHB2: Versatility over the animal stat buffs, traded for half the power. It's a style thing; either way is good.
Barkskin: Excellent for use while Wild Shaped, since your AC will often be pretty poor.
Bear's Endurance and Bull's Strength: As useful as it is for everyone. Bear's Endurance will be your main in-combat healing spell for low levels; just keep people alive until you can use Vigor.
Bite of the Wererat^SpC: A variety of handy stat buffs, plus an additional bite attack for forms that don't have a natural bite.
Blinding Spittle^SpC: Absolutely broken. Blindness with no save, with a ranged touch attack at:4. Why do they keep reprinting this spell?
Blood Snow^Frost: Only prep it during the winter or when in an arctic or otherwise frozen area, but d2 Con damage/round is awesome.
Brambles^SpC: Excellent weapon buff, especially coupled with Shillelagh.
Briar Web^SpC: A handy entangling spell that may also cause damage.
Creeping Cold^SpC: A great attack spell, and replaces produce flame.
Desiccate^Sand: d6/level (max 5d6) on a single target, with a weird damage type that ignores DR and energy resistance. Can even cause dehydration (which is fatigue on steroids).
Earthbind^SpC: Ground those fliers.
Embrace the Wild^SpC: and Listening Lorecall^SpC: Hopelessly nerfed in Spell Compendium. Unless you really, really need Scent for something, Blindsight is just plain better, save for duration. Embrace the Wild is generally better because of the skill boosts, until you have 12 ranks in Listen, when Listening Lorecall's Blindsight kicks in. Either way, Blindsight is worth it, despite the higher spell level.
Gust of Wind: Very underrated utility spell. Clears fogs, blows away small foes, extinguishes torches, and disperses swarms.
Halo of Sand^Sand: Yet another druid AC buff. This one is deflection, though, so it stacks with Barkskin and armor.
Kelpstrand^SpC: I like to think of this spell as webshooters. This spell is excellent for tying down not-particularly-strong foes, and remember that you can throw multiple strands on one target. The low grapple DC and the slow scaling for multiple strands means that this spell goes stale quickly, however.
Lesser Restoration: Very handy for healing ability damage.
Luminous Armor^BoED: An AC boost while you're Wild Shaping, plus light and another -4 for enemies to hit you in melee. Stacks with Barkskin, but not Wilding armor. Mind the Str damage, though.
Master Air^SpC: Self-only flight, with short duration. Still handy, though.
Nature's Favor^SpC: Excellent (swift!) animal buff spell; cast it on your Animal Companion or summons. Technically better than Greater Magic Fang, but has a shorter duration and doesn't bypass DR. The Complete Divine version is even stronger, but the spell was nerfed in Complete Adventurer.
Resist Energy: Fairly handy when you know a certain type of energy damage is in the offing.
Share Husk^SpC: A great scouting spell. Use it if Spider Hand isn't available.
Snake's Swiftness, Mass^SpC: The lower-level, single-target version of this spell isn't anything special, but giving a free attack to all of your party members, plus your animal companion, plus any summons you have nearby is just too fun.
Splinterbolt^SpC: its the druidic scorching ray, but with no SR (and coupled with a nice high dex animal form, (e.g., Legendary eagle) its nearly as easy to hit with). 4d6 x3 with a 18-20 threat range isn't half bad. thanks jackmojo
Wild Instincts^RoE: +1 to spot + listen just for preparing it, swift cast for +10 to both and retain dex when flatfooted or vs unseen opponents for min./level.

3rd Level

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Alter Fortune^PHB2: Fantastic spell. Great for emergencies (reroll a save!)
Arctic Haze^Frost and Haboob^Sand: Damaging and opaque fog. Useful as battlefield control. Tremor^SpC: can be used similarly, but it doesn't damage and doesn't block line of sight.
Attune Form^SpC: Immunity from planar effects for caster level/3 characters. A handy spell for high levels, and much more useful than the lower-level Avoid Planar EffectsSC: due to the longer duration.
Bite of the Werewolf^SpC: Again, a variety of nifty stat buffs and a spare bite attack.
Blindsight^SpC: 30' Blindsight. Who needs See Invisibility?
Call Lightning: Good damage, and gives you plenty of turns of attacks. The attack spell you'll be using when you get 3rd-level spells.
Crumble^SpC: Think of this as druidic Knock. Lots of things won't stand up to a casting of this spell.
Cure Moderate Wounds: Should be self-explanatory.
Energy Barrier^{Key of Destiny}: It lets you put up an immobile protective barrier against acid, cold, electricity, fire, or sonic energy and their residual effects (e.g. fire: also blocks heat, acid: water, cold: snow, etc.). This amorphous barrier can completely surround you if you like and the duration is "concentration +1 round/level," which could be huge in some circumstances.  If your DM allows Dragonlance materials, this is a great protective spell.
Entanging Staff^SpC: Free action grapples with a +8 bonus. Great for when you're out of Wild Shape for some reason or if you're using a Spikes-enspelled staff as a Legendary Ape.
Evard's Menacing Tentacles^PHB2: To the extent that you have a good strength bonus, this spell provides some battlefield control and meets out some damage and gives a climbing bonus to boot
Forestfold^SpC: +10 on Hide and Move Silently checks in a natural environment of your choice.
Giant's Wrath^SpC: An interesting alternative to Call Lightning. At early levels, the lack of a need for an attack roll, the lack of DR issues, and the greater number of uses per cast makes Call Lightning the better choice. At higher levels, though, the high strength of Wild Shape forms, the caster-level based damage bonus, and the lack of SR on Giant's Wrath helps it catch up.
Girallon's Blessing^SpC: This spell gives the creature touched an extra set of arms for 10/minutes per level, which can be quite handy if your wildshape form could use some arms to manipulate objects.  There are probably better ways to mete out damage, but solid choice if you think your shark form may need to open a door, chest, etc.
Greater Magic Fang: Handy self-buff and good to share with your Animal Companion.
Junglerazor^SC: Does 1d10/level (up to 10) in a 120ft line. Because it's target specific, shoot through your friends to damage only plants, plant critters, vermin, fey and animals.
Plant Growth: A powerful battlefield control spell (or a nice way to help the local economy) in the right circumstances.
Poison: Con damage is always handy, and the DC scales upward as you increase in level. A much-overlooked spell.
Primal Form^SpC: This spell isn't overwhelmingly powerful, but it's a versatile self-buff. Flight and swim speed are easy to get with Wild Shape, but this spell is available before plentiful Wild Shape uses, and you can choose on the fly among a melee buff, a defensive buff, or a source of flight.
Primal Instinct^DrM: +5 competence bonus to Initiative (and Survival) for 24 hours.   
Protection From Energy: A versatile, effective defensive buff. You'll rarely regret prepping it.
Remove Disease: Not something you're going to prep every day, but handy when you need it.
Sleet Storm: Handy battlefield control. Great for covering an escape. Not as good as Arctic Fog or Haboob, though.
Spiderskin^SpC: Barkskin, plus a save bonus against poison and a Hide bonus. Use it on the party sneak, or when you're fighting monstrous vermin or Yuan-Ti.
Spikes^SpC: Improved Brambles. Higher attack, better threat level; what's not to like?
Spritjaws^SpC: I love this spell, and it's one of a druid's few good force spells. Throw this spell out there and it's a combination of Spiritual Weapon and Telekinetic Grapple. It damages and confounds enemies, doing an especially good job of pinning down spellcasters and incorporeal foes.
Stone Shape: Good for making your own entrance or exit. Great for throwing the GM a loop in a dungeon crawl.
Swift Lion's Charge^MiniHB/Lion's Charge^SpC: Pouncing is very handy, but this spell can start to eat up spell slots pretty quickly. A similar, overpowered spell named Lion's Charge is in Savage Species, and, while it isn't swift, it gives the Pounce ability for a duration.
Thornskin^SpC: Good as a wildshape buff, especially for grapplers, since even trying to escape hurts your enemy.
Touch of Jubilex^BoVD: Evil. A great early save-or-die. Whatever it is, in four turns, it'll be dead. Not something you can safely use repeatedly, though, because of the Corruption cost.
Venomfire^SK: Ridiculously broken spell at high levels. For level/hours, +d6/level damage with no cap added as an additional effect to a poisonous natural attack. Great for Fleshraker Wild Shape, or a poisonous breath weapon or AoE effect.
Vigor and Mass Lesser Vigor^SpC: Both can be better than Cure Moderate Wounds at low levels, but only outside of combat. It works when you can't summon Unicorns yet and you don't have that handy wand of Cure Light Wounds. Doesn't work with Extend Spell (see CD FAQ), but Mass Lesser Vigor does work with Persistent Spell.
Wind Wall: Another highly underrated spell, this stops archers, swarms, and foes size Tiny or smaller cold.

4th Level

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Arc of Lightning^SpC: A decent no-SR spell, with damage competitive with that of a wizard or psion. It's a conjuration spell, so, that Spell Focus: Conjuration feat you had to pick for Augment Summoning might be useful.
Aspect of the Werebeast^RoE: Nothing about this Shifter-only self-buff says it only works when you're in a humanoid form. Add +4 to two different attributes, and add Improved Grab, Pounce, or wolf-like Trip to whatever form you're in.
Bite of the Wereboar^SpC: Useful stat buffs, a spare bite attack, and one of the better AC buffs around.
Blast of Sand^Sand: Cone of Cold lite (cone, d6/level, max 10d6), only without the energy type. No SR!
Boreal Wind^Frost: Does decent cold damage, has a fairly big AoE, blows enemies away, disperses fogs and swarms, and keeps going for multiple turns without concentration. Compares favorably even to Flame Strike.
Claws of the Savage^BoVD: Got claws? This gives you a +2 enhancement bonus on them, and also gives increases your claw damage as if you were two sizes larger. It is an Evil-typed spell, though.
Enhance Wild ShapeSC: You can pick up plant forms early or get minor stat buffs, but the big bonus is the access to extraordinary abilities. Pick up the Blindsight of a Desmodu War BatMM2, or abuse Master of Many FormsCAdv.
Flame Strike: Excellent damage and an AoE. Should replace Call Lightning as your attack spell of choice.
Freedom of Movement: Makes you immune to grapples, able to fight underwater, and immune to spells that impede movement. A very handy defensive spell.
Giant Vermin: Ridiculously powerful at high levels: at level 20 you can make a 40 HD monster.
Greater Luminous Armor^BoED: As Luminous Armor, only +8 AC instead of +5. Again, mind the Sacrifice cost.
Heart of Earth^CM: Temp HP for hours/level, but the real value is that you can end it early for a component-less Stoneskin as a swift action.
Hibernal Healing^Frost: Self-only Heal...as long as you're in a frostfell area, anyway.
Last Breath^SpC: In Complete Divine, this is druidic Revivify, but with a caster-damaging side effect. In Spell Compendium, this is a no-level-loss Reincarnate that must be cast immediately. Both are useful as an emergency option.
Passage of the Shifting Sands^DrM: Druidic Gaseous Form, but with an actual move speed, the ability to blind people, and other bennies.
Scrying: The gold standard in sneaky divinations.
Sheltered Vitality^SpC: Immunity to ability damage or drain is situational, but very powerful when you need it. Cast this before fighting yuan-ti, giant vermin, undead, or anything else with a nasty ability damage or poison attack. The immunity to fatigue can also be handy for the party barbarian.
Superior Magic Fang^SpC: GMF on all of your attacks. It's self-only, though.
Unholy Beast^CoR: This is an odd one. It's a lesser, single-target Animal Growth...but with a Dominate Animal effect tossed in. Great for stealing Animal Companions, but still usable as a general-purpose buff.
Vortex of Teeth^SpC: A spell that does force damage, and can tear apart anything that can'tget away. This makes a mess of anyone caught in Entangle.
Wall of Salt^Sand: Not quite Wall of Stone, but effective for battlefield control and deterring pursuit.
Wind at Back^SpC: It lets you double the party's overland speed, lasts 12 hours and can let you speed up multiple beasts of burden, as well.

5th Level

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Animal Growth: Multiple animalsyour pet and any summons running around) get bigger and get some nice bonuses. One of the best buffs in the game, let alone in core.
Anticold Sphere^SpC: Immunity to cold and great protection from anything with the Cold subtype, with a nice long duration and an area large enough to protect the whole party.
Baleful Polymorph: Turn your opponent into something inoffensive. Toad and cat are both classy forms that offer no advantages to your target. Also handy for transporting oddly-sized Animal Companions or water- or air-breathing Animal Companions Pokemon-style, since, as a permanent spell, it's dispellable.  Classy tricks include polymorphing your Roc Animal Companion into a raven for cramped quarters, or polymorphing your T-Rex companion into a frog to go underwater.
Bite of the Weretiger^SpC: A very high str boost, a variety of other boosts, extra attacks, and free Power Attack.
Blizzard^Frost: Instant battle ender. Great for buying some time to parley or obscuring your plans. Huge area of effect.
Call Avalanche^Frost While it doesn't cause overwhelming damage (only 8d6), it can bury many opponents in its huge area (size of creatures you can bury scales up as well). It only works outdoors, but it does damage and potential immobilization at long range. For a good trick trick, follow it up with Blood Snow and all the poor buried victims start taking CON drain while trying futilely to escape.
Call Lightning Storm: Call Lightning, only more so. 5 dice of damage instead of 3.
Choking Sands^Sand: Miasma, only less so. Alternately, nonpsionic Crisis of Breath. Good for shutting down a caster for a turn.
Cloak of the Sea^SpC: When you're underwater, it's Water Breathing, Freedom of Movement, and Blur, all in one neat little (long-duration!) package. A must-have for any underwater adventures.
Control Winds: Gets you a minimum of hurricane force winds (assuming no wind when you cast it) at Caster Level 13, which covers a 520ft radius, lasts for over 2 hours, and slaughters medium enemies while stopping anything smaller then gargantuan from doing anything useful. And again as soon as you hit 15 its gets even worse, cause you get tornado winds, which will stop anything and destroy cities and non fortified structures.
Death Ward: Powerful, if conditional, defensive buff.
Owl's Insight^SpC: A long-duration scaling boost to Wisdom with an unusual bonus type? Yes please.
Pancaea^SpC: A broad-based restoration spell, removing pretty much any condition other than ability damage/drain, disease, or death.
Phantom Stag^SpC: Conjure a very fast mount that it gains a lot of useful additional effects based on caster-level, so that even though its only level 5 its well, it's worth preparing at higher level still, since it, for example, can make you ethereal (as the 9th level cleric sor/wiz spell). (thanks jackmojo)
Quill Blast^SpC: After the Spell Compendium rewrite, this once-broken spell is now not quite as hot. It still outperforms typical blasts for a couple of levels, but by level 9 blasting is probably not the most optimal thing to be doing. It is a really mean spell for a GM to use on the PCs, though.
Rejuvenation Coccoon^SpC: A decent out-of-combat Heal alternative.
Ice Shield^Frost and Stoneskin: Excellent defensive spells (Ice Shield is stronger but has a shorter duration), but both are too monetarily expensive to use too often.
Tree Stride: Poor man's Teleport. Saves on overland travel time, but that's about it.
Wall of Thorns: This is a nice battlefield control/stop pursuers/obstruct sight spell, with nice size and a nice duration.  Not always useful, but sometimes key.  Of course, if you're summoning Greenbound creatures, choose something else.

6th Level

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Antilife Shell: Exceedingly powerful defensive spell. Anything living without SR just can't touch you.
Bite of the Werebear^SpC: Bite of the Weretiger only moreso.
Chasing PerfectionPHB2: Handy as a self-buff, since it's hard to use magic items in Wild Shape. Won't be terribly useful to the rest of the party at level 13, though.
Drown^SpC: Save or dying (0 hp). Handy for capturing enemies alive. Not death magic, but obviously doesn't work on non-living creatures, water-breathers, or creatures with no lungs. This has replaced the repeatedly-nerfed Miasma^SpC.
Energy Immunity^SpC: Powerful, of a bit situational, defensive buff. Has a long enough duration to have it on all the time.
Enveloping Cocoon^SpC: This will let you turn the save of any number of nasty spells (Miasma and Baleful Polymorph being the nastiest) into a Reflex save, essentially, or just tie up one enemy that doesn't have a light/natural weapon handy (including incorporeal foes).
Find the Path: Never, ever, EVER be lost.
Fire Seeds: Excellent trap spell when used to make holly berry bombs. Couple it with some sort of fire resistance or immunity and you have a killer emanation-from-yourself nuke.
Fires of Purity^SpC: A hefty melee damage buff, plus Flame Shield lite. Note that, while this spell is three levels higher than Venomfire and only adds one point per caster level instead of d6, it's still a good spell. That's how silly Venomfire is.
Greater Dispel Magic: Unlike mages and clerics, druids very rarely lose caster levels, so this is often a worthwhile spell to prep.
Greater Scrying: Scrying without the long casting time and relatively short duration; the minor spells you can cast through the sensor aren't that useful.
Liveoak: Handy if you need a Treant to guard your camp or home. The casting time and casting limitations limit its general usefulness, though.
Mummify^Sand: Save or die. Plus, it's not death magic.
Spellstaff: One extra spell slot, of whatever level you can cast. Clerics with Miracle have no reason not to duplicate this very handy spell.
Superior Resistance^SpC: +6 on all saves, all day. Its utility is obvious. (Spell Compendium upped the level, but also the duration. It's still worth it, unlike the pounding Major Resistance took.)
Tortoise Shell^SpC: Basically, Greater Barkskin. Not as good as Greater Luminous Armor, but is natural armor instead of armor.
Valiant Steed^BoED: Calls a Unicorn or Pegasus that serves you for an entire year.

7th Level

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Constricting Chains^BoED: Whatever it is, it's entangled and can't move. No save, no SR. Unless it has at least a +20 Escape Artist mod or a 34 Strength, it's staying stuck unless it wears down the chains with attacks (and half of that damage is in turn redirected to the chained target). Mind the Sacrifice cost, though (which doesn't take effect until the spell ends).
Cry of Ysgard^BoED: Calls 2d4 defenders of Ysgard that serve for a year.
Death By Thorns^BoVD: The Corruption cost is very painful, but this will take the target out of the fight, no matter what. Obviously an evil spell.
Heal: Its uses are obvious.
Master Earth^SpC: Quite nice as it allows teleportation, a rarity for druids, without chance of error to any location touching the earth, and also  it doesn't have the teleportation descriptor so it can thwart problems such as forbiddance, dimensional anchor/lock, etc.
Rain of Roses^BoED: Continuing Wisdom damage over an area, to evil creatures only. Great if you can limit the target's mobility, as the Wis damage doesn't allow a save.
True Seeing: Magic bullet for illusions, invisibility, and shapechanging.
Word of Balance^SpC: Somewhat unreliable because of the odd alignment restrictions, but very powerful when it works.

8th Level

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Cocoon^SpC: Lets your Cleric buddy cast true resurrection 2 levels earlier, or if you don't have friends lets you reincarnate with no level loss a week later; it has an XP cost, but it's negligible at best at this level.
Frostfell^Frost: Caster level/20' cubes freeze, and anyone in this area rolls a Fort save or turns to ice (and still takes caster/d6 frostburn damage if they save). Think of it as shapable super druid Wail of the Banshee, with an extra heaping helping of awesome.
Leonal's Roar^BoED: Druidic Holy Word, plus some sonic damage. Sweet.
Stormrage^SpC: Flight, the ability to throw respectable lightning bolts, and immunity to projectile ranged attacks and wind effects of all kinds.
Word of Recall: A quick escape spell, and one of the very few teleportation spells available to druids.

9th Level

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Nature's Avatar^SpC: Very, very powerful animal buff, and now a swift spell. Cast it on your Animal Companion, and go to town.
Shapechange: Broken spell, but you already know that. Ridiculously powerful, even if you don't abuse the ChronotyrynFF or Choker or Efreeti or ZodarFF or...well. You get the idea.
Summon Elemental Monolith^SpC: The elemental monoliths are ridiculously powerful, especially given the very high save DCs of the whirlwind and vortex abilities of air and water monoliths.  This spell's true value comes to life when you have the skill trick Swift Concentration.
Tsunami^SpC: The fight is over. This spell will end anyone smaller than Gargantuan who can't immediately get out of the way of the 40-ft-high wave. The spell component is rather expensive, however.
Undermaster^SpC: Awesome power indeed. This gives you a whole variety of great spell-likes, some of which aren't even on the druid list.

Summon Nature's Ally
Druids have the ability to spontaneously cast Summon Nature's Ally, making memorizing the spells pointless. Given the short duration of these spells and the disposable nature of summoned creatures, you're going to want to use them as distraction and cannon fodder. Speak With Animals is especially handy when you're summoning animals, as it allows you to direct them to flank, concentrate on particular foes, or do other useful things other than "attack closest foe or biggest threat."

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    Summon Nature's Ally 1
        Wolf: Not much worth summoning at this level, so the wolf is it.
    Summon Nature's Ally 2
        Crocodile: Unless the foe is small enough to grapple, have it slap with its tail.
        Hippogriff: A little less hard-hitting than a croc, but it flies and you can talk to it. No animal buffs, though. (Bonus style points for having it grapple a foe and fly up until the spell runs out.)
    Summon Nature's Ally 3
        d3 Crocodiles: An ad-hoc swarm of crocs is great for shutting down spellcasters or other weaker, grappleable or low-AC foes.
        Dire Wolf: Other than the low AC, this is an all-round combat superstar.
    Summon Nature's Ally 4:
        d3 Dire Wolves: Dire Wolves hit hard enough and have enough HP to make them useful in numbers.
        Brown Bear: Hits hard enough to be on the front line, and grapples spellcasters and such. Oh yeah.
        Giant Crocodile: Compared to the Brown Bear, it has one big bite instead of multiple medium hits, with better grappling to make up for the lesser damage. Whether you use this or Brown Bear is a matter of style.
        Tiger: Another Brown Bear alternative. Slightly less damage in a straight fight and a slightly lower grapple check, but does more damage when charging or when in a grapple.
        Unicorn: Summon Unicorns for on-the-spot healing. Three uses of CLW, a use of CMW, a use of Neutralize Poison, and at-will Detect Evil. Plus, it can bypass DR X/magic and is smart enough to talk to.
        Yellow Musk Creeper^FF: A very unusual summon, Yellow Musk Creepers are super-tough (good HP plus Regeneration), have Blindsight, and can use their Musk Puff ability to enthrall and devour anything with a bad Fort save. Just don't expect them to do any straight slugging, with their weak attacks, or keep up with fast-moving foes, due to their near-inability to move.
    Summon Nature's Ally 5:
        d3 Brown Bears (or Giant Crocodiles or Tigers): A pack of grapplers can shut down many foes and outstrip even a single Polar Bear.
        Large Elemental: This is where Elementals start to get good. Earth Elementals will be your general-purpose tanks (although Fire Elementals can fill this role equally well), and double as caster-killers if you have Rashemi Elemental Summoning (UE). Air Elementals are great for shutting down swarms of mooks, fliers smaller than they are, and casters, but aren't quite as hard-hitting as the other Elementals. (Remember, a Large or larger Air Elemental in Whirlwind form counts as a storm for Call Lightning and Call Lightning Storm.)
        Rhinocerous: Very deadly if summoned with room to charge an enemy.
    Summon Nature's Ally 6:
        Huge Elemental: A single Huge Elemental is worth more than three smaller ones. Keep using this in the same way you used the Large ones.
        Large Storm Elemental^MM3: Think of it as a Fireball and a summon, all in one. Storm Elementals aren't quite the fighters the other Elementals are, but the first turn they are summoned, they do 12d6 damage to everything in 60 feet (plus 4d4 nonlethal to a single target) instead of attacking normally. Make sure you speak Auran to keep it from blasting your allies, or else be careful where you summon it.
        Dire Bear: Tears casters to bits. Great for anything that can't handle its +23 grapple mod, not so great for anything else.
        Elephant: Raw damage machine. Not as tough as a huge Earth Elemental, but hits very hard or tramples mooks.
        Oread^FF: Not a melee monster, but has an awesome array of spells, including Transmute Rock to Mud, Stone Shape, and Earthquake(!). Don't ever bother prepping Earthquake if you can just summon an Oread.
        Pixie: Not much in melee, but can cast Dispel Magic (poorly but repeatedly) and Detect Thoughts for you.
    Summon Nature's Ally 7:
        d3 Huge Elementals: Greater Elementals are only marginally better than their Huge counterparts.
        Huge Storm Elemental^MM3: A Huge Storm Elemental is significantly better than even two or three Large ones.
        Pixie (w/sleep arrows)
    Summon Nature's Ally 8:
        d3 Greater Elementals: A pack of Greater Elementals far outstrips any of the limited choices at this level.
        Greater Storm Elemental^MM3: Definitely better than a Huge Storm Elemental.
        Sporebat^FF: A very specialized choice, this is good for Enervating foes you can't otherwise hurt. Otherwise, they're pretty wimpy.
    Summon Nature's Ally 9:
        d4+1 Greater Elementals: Elder Elementals are marginal at best.
        d3 Greater Storm Elementals: Think of it as spontaneous druidic Meteor Swarm, only it leaves Greater Elementals in its wake. A fun tactic: have them stagger their use of Thunder And Lightning to heal each other if they take damage.


Aquatic Summons
If you're underwater, you might want to instead summon...

    Level 1:
        Porpoise: Not exactly a combat dynamo, but it's something. Blindsight is handy in the dark depths at the ocean's floor (I always wanted to use that line) or against invisible foes.
    Level 2:
        Crocodile: Just as good in the water as it is on dry land.
    Level 3:
        d3 Crocodiles: None of the other options are worth fiddling with.
    Level 4:
        Giant Crocodile: A great all-rounder, especially underwater.
        Sea Cat: The underwater equivalent to the Brown Bear, only with Rend instead of Improved Grab.
    Level 5:
        d3 Giant Crocodiles: A pack of killer crocodiles is still your best combat summon.
        Large Water Elemental: The Water Elementals don't become as dominating as their Earth equivalents on land, but Vortex shuts down spellcasters and mooks cold and DR 5/- frustrates lesser foes.
        Orca Whale: Lacks the Improved Grab of the Giant Crocodile, but has Blindsight and more HP.
    Level 6:
        Huge Water Elemental: NOW we're talking. Huge size is when Water Elementals come into their own, and get the AC and HP to stand (swim?) on the front line while maintaining the ability to shut down lesser combatants with a Vortex.
    Level 7:
        d3 Huge Water Elementals: Greater Elementals only get marginal improvements over their Huge predecessors.
    Level 8:
        d3 Greater Water Elementals: Like Earth Elementals, but underwater, get it?
    Level 9:
        d4+1 Greater Water Elementals: For the same reasons you were summoning them last level.
        Octopus Tree^FF: The Fiend Folio strikes again. This critter has nine competent attacks, Improved Grab and Swallow Whole, a (mostly useless) frightful presence ability, Quickened spell-likes, and Regeneration to boot.

Greenbound Summoning
If you took Greenbound (LEoF), things are a bit different. Obviously, you're going to want to summon animals, and the bonuses make multiple lower-level creatures, particularly grapplers, more powerful. As such, you'll spend a lot of time summoning d3 grappler creatures. Remember, you can still summon utility creatures like Unicorns or Pixies. They just don't benefit from Greenbound.  If you cast Speak With Plants, you can have your Greenbound summons cast Entangle or Wall of Thorns for you. Take advantage of this!

[Mooncrow]

Animal Companions

The second leg of the druid Triad of Power, the Animal Companion is a vital part of what makes a druid.  A properly built companion can function as almost another party member (or even make the poorly optimized fighter cry, depending on your group ), but the key to getting the most out of your furry (scaly/feathery) friend is choosing a role for them and stick to it.  Companions aren't druids themselves; they can't do everything   So, what are the roles that companions can do well?

Grappler - best served by a pet with all-around good stats, the grappler gets into the thick of things.  Yes they do some damage, but more importantly, they lock down one or more of the enemy, while serving as a barrier to others.  This is really valuable if you spend a lot of time dungeon crawling, or fighting in places without a whole lot of space.  Crocodiles, bears and some of the dinosaurs make the best grapplers.

Pouncer - the pure damage dealing option.  Pouncers all do full attacks on a charge, and often a few extra attacks as well.  The downside is that most of them are pretty fragile and they require a fair amount of space to do their thing.  But when properly buffed up, a pouncer can put serious hurt on the bad guys.  The alternate method is the Charger - they usually have one big attack and Powerful Charge for double damage.  If they have trample, they can charge in, trample, move away as part of the trample, and then charge back in (the infamous Triceratops Shuffle, as it's known).  It requires even more room though, and it's a bit too conditional for my tastes.  For pouncers, look for the big cats and raptor dinosaurs for the power.  For chargers, look for the horned dinosaurs and rhinos.

Mount - You're no paladin, but that doesn't mean you can't use your companion for a mount.  Now, I do think it's a waste to just use your companion for a mount.  While it is an easy way to get flight, there are other ways to get that - there aren't a lot of ways to get another loyal-unto-death combatant.  If you're going to go the mount route, make sure it fits with your own combat style.  Being mounted means that it's easy to take advantage of Share Spell, so you could, for example, grab a lance, and charge in on a Charger to do all sorts of ridiculous damage.  There are lots of companions that work as mounts - just make sure it's one size larger than you.

Dire Tortoise - it doesn't really fit in with the other categories, but it's still incredibly good.  Huge HP, great AC, good trample, and an auto-surprise round make for a surprisingly effective pet.  I've never been disappointed by this guy.

Now that you know what role you want to focus on, it's time to pick out your companion. 

To level up, or change companions?
Probably the most frequently asked question.  Do you swap out your pet every three levels, or let it gain the bonuses from leveling?  Generally speaking, it's better to swap them out.  There are exceptions, but most of the time, you gain more from a higher level base pet.  Now, if you do stick with the same pet, there are a couple advantages.  1. it will end up with higher AC - most base animals tend to stay in the 14-17AC range, regardless of level.  2. you get to select its feats. 

Most of the time, that's not enough to make up for the increased damage, number of attacks, increased size, etc.  The exceptions:  Fleshraker - it's good enough that it can last you pretty much your whole career, and if venomfire is allowed in the campaign, it's hands down the best selection all the way to 20.  Magebred Bear/Ghost Tiger - the boosts this template give you, combined with the generally poor selection at level 10 means that it's worth it to hang onto them until at least 13 and possibly until 16.  Dire Tortoise - it's base stats are so high, and it's so unusual, that if you like it, it can serve until 20 without any problem.

On to the lists!

Level 1

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Core
   

• Badger: Has multiple attacks but that's pretty much all it has going for it.  Also, good luck getting it's rage ability to go off before it's dead
• Camel: If you're looking for a companion to be just a non-combat beast of burden, this is the best first level choice.  Don't waste your class feature on that though - if you want a mount, the heavy horse is better in every way except for carrying capacity.
• Dire Rat: extremely fragile, low damage and the disease is worthless.  One of the worst options available. 
• Dog: the Riding Dog is superior in every way.  Don't take this.
• Riding dog: Make sure yours is trained for war, per the monster entry. Tough, relatively hard-hitting, can wear barding without wasting feats. Superior in every way to a wolf. Good mount (small druids only) and substitute low-level tank if you give it barding.  Probably the best first level choice.
• Eagle: Fast flight speed and multiple attacks make this a not horrible choice if you're looking for a scout.  Very low hp though, so combat is very dangerous for them.
• Hawk: Inferior to the eagle in every way.
• Light Horse: Faster than a heavy horse, but weaker.  The heavy horse is probably the better over-all choice if you want a companion of this type.
• Heavy horse: Fast mount for medium druids. Large.
• Owl: Get an eagle if you want a flier.  The Move Silently bonus is not worth giving up all offensive capability.
• Pony: Get a horse if you want a mount. 
• Snake, Small/Medium Viper: slow, weak, fragile.  Even with Venomfire these guys wouldn't be worth using.
• Wolf: It is strictly worse than a war trained riding dog, but even so, it's not a terrible choice.  If you're looking for a decent attacker and don't like the riding dog flavor, this guy is alright.

Non-Core
   

• Brixashulty^RoW: Halfling-only.  Very close to a riding dog; gives up a little damage for higher Con, and trades the trip for a knockback.  Solid choice.  Non-halflings can get these at level four - don't bother.
• Caribou^Frost: Strictly inferior to several other choices.  Low speed for a mount, medium sized, low damage.  Pick something else.
• Chordevoc^RoW: Halfling-only.  Better than an owl, but stat-wise, inferior to an eagle.  The only potential saving grace is its 60' Blindsense.  Not a strong option, but it does have it's niche if you need an early sentry against invisible assassins. Non-halflings can get these at level four - don't bother.
• Climbdog^A&E: A wolf without the trip attack.  I guess the massive climb bonus could come in handy is some campaigns - but for the other 99.99% of druids, get something else.
• Jackel^Sand: Literally identical to the dog entry. 
• Serval^Sand: Actually a pretty decent damage dealer.  The only first level pouncer, with three attacks and has Improved Grab and a Rake attack.  On the downside, it's Small, so it's unlikely that its Grab will work, and with 5 hp, combat is not a safe place for it.
• Swindlespitter Dinosaur^MM3: Harasser with paralyzing AoE attack
• Vulture^Sand: Inferior in every way to the eagle. 
  

Level 4

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Core
   

• Ape: Decent hp, 3 attacks; nothing to get real excited about, but a decent choice.
• Dire Badger: Much better than the non-dire version.  This one can actually be a decent option.
• Dire Bat: Flying mount for medium druids.  Good hp and decent AC.  Large.
• Black Bear: Inferior to the ape in pretty much every way. 
• Bison: A sack of hp with not much else going for it.  Avoid.
• Boar: Another weak choice.
• Cheetah: Its speed is the only thing it has going for it.  If it had Pounce it might be a decent option, but it doesn't, so it's not.
• Crocodile: Grappler and general slugger. (PHB 3.5 and PHB2 confirm that this is a level 4 choice. The SRD lists it as available at level 1 for aquatic druids; the SRD is wrong in this case.)
• Leopard: Solid damage dealer, but a bit fragile like all cats.  Has Pounce, Improved Grab and Rake.  If you like cats, this is the best cat for the level. 
• Monitor Lizard: No. 
• Snake, Large Viper/Constrictor: Still bad.
• Dire Weasel: Its Drain attack is too slow to make up for its abysmal overall stats.
• Wolverine: It's not quite as good as the ape, but if size is a major factor in your campaign, this is the best core medium animal.

Non-Core
   

• Fleshraker Dinosaur^MM3: Pouncer/tripper/grappler with poison.  Far and away the best companion at this level, and possibly the best companion, period.
• Axebeak^A&E: one of the better ground mounts.  Fast, decent hp, and reasonable attacks.
• Dire Hawk^RoW: Raptoran-only.  A solid defensive creature with decent AC and hp.  Their attacks are nothing to write home about though. Non-Raptorans can get these at level 7 - but don't bother.
• Horrid Rat^ECS: This first of the Horrid options, this one isn't quite good enough to use.  1HD just isn't enough.
• Sailsnake^MM4: A fan of Alan Dean Foster's Flinx series?  Now you can have your own Pip, venom spitting and all.  Overall, not very strong unless you're using venomfire - a very good option if you are.
• Dire Toad^MM2: it's poison is ok, but probably not enough to make up for it's weak base attack.  Its Swallow Whole ability is pretty much useless as well.
• Watchspider^CoS: An interesting option for those wanting to use venomfire without a fleshraker.  It's not a very strong companion, but it is the only magical beast available without a feat or PrC.  It's tremorsense could be potentially useful as well.

Level 7

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Core
   

• Dire Ape:  It gets a Rend attack that does decent damage, otherwise very similar to its non-dire version.  Really low hp for this level.
• Brown Bear: Grappler. Not as good in a grapple as Giant Crocodile, but better-rounded and harder-hitting in a straight fight. Large.
• Dire Boar: A lot of hp and Str and the Ferocity can be nice, but a single attack just isn't very good by this point.
• Giant Crocodile: If you're looking for a dedicated grappler, then this is your guy. Inferior to the bear for anything else though.  Huge.
• Deinonychus: Pounce and four attacks balances out the abysmally low hp.  Still inferior to the tiger however.
• Lion: Like a tiger, but not as good.
• Rhinoceros:  High hp and Powerful Charge make this a not terrible option.
• Snake, Huge Viper: Like the rest of the snakes, still terrible.
• Tiger: Pounce, multiple attacks, Improved Grab and a Rake attack with decent hp.  If you're limited to Core-only, it's a toss up between this guy and brown bear for the best of this level.
• Dire Wolf: The wolf was decent at level 1, but by this point, one attack + Trip doesn't really cut it.
• Dire Wolverine: Its Rage ability in no way makes up for its lower damage and lack of Pounce compared to the other options available.

Non-Core
   

• Horrid Badger^ECS:  Low HP, but very good damage, and its high AC does help out with the survivability issue.
• Horrid Bat^ECS: Excellent AC, and by now, the Con boost from the Horrid template is starting to partially make up for the low HD.  Not an option I would choose, but a decent flying mount.
• Magebred Brown Bear^5N: A straight upgrade to the already good brown bear.  A very attractive option.
• Cave Anklyosaurus^MiniHB/PHB2: A tough trampler that hits almost as hard as a Giant Crocodile. Large.
• Dire Eagle^RoS: Flying mount for medium characters, for games where Horrid animals aren't available. Large.
• Megaloceros^Frost: Really bad. Not quite as bad as say, a snake, but still not worth taking.
• Protoceratops^Sand: Even with Powerful Charge, this thing is terrible.  A rhino is superior in every way.
• Terror Bird^FF: Flesh-eating ostriches are cool and all, but aside from its higher than normal initiative, this is not a good choice.
• Magebred Ghost Tiger^5N: Hard-hitting and tough pouncer. It's only arguably better than Fleshraker. Large.
• Horrid Weasel^ECS: Nope.  The weasel is too weak for even this template to save.

Level 10

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Core

• Polar Bear: Aside from its swim speed, it's inferior to just staying with the Brown Bear in every way.
• Dire Lion: Almost identical to a leveled up tiger, except that the tiger has better feats.
• Megaraptor: If size isn't an issue, this guy is ok - he would be a lot better if he had more than one primary attack, and he lacks the grab/rake combo of the cats.  Fairly durable for a pouncer though.
• Giant Constrictor Snake:  Odds are good that you know the answer to this already: snakes are not good companions, period.

Non-Core
   

• Allosaurus^MM2/PHB2: Hard-hitting grappler and quite passable trampler. (Not as good at trampling as the Dire Tortoise, though.) Huge.
• Horrid Ape^ECS: The dire ape's low base HP makes this template a bad fit.
• Bloodstriker^MM3: An offensively- and defensively-balanced choice. (Don't mistake it for a game-balanced choice. It eats melee attackers alive.) It has tons of HP and decent AC, but can still deal respectable damage (especially with Powerful Charge). Plus, anyone who tries to attack it in melee will take a dozen damage per hit.  Top it off with a breath weapon and it's a very reasonable choice.
• Horrid Boar^ECS: Only having one attack really doesn't cut it.
• Dragonhawk^5N:Fast flying mount, with Blindsense and some fairly decent attacks. It's big enough to carry several party members, depending on encumbrance. Huge.
• Glyptodon^Frost: As cool as having a pet giant armadillo would be, he's not a very good companion.  DR 5/piercing doesn't make up for the very low damage output, and surprisingly low AC.  Avoid
• Hippopotamus^Sand: Despite how deadly as these guys are in real life, they aren't very deadly in D&D.  Low AC, low speed, one attack - even the above average feats that it has can't make up the shortfall.
• Dire Horse^MM2: Even if you're just looking for a mount, you can do way better than this.
• Horrid Horse^ECS: However, when you throw the Horrid template on the terrible dire horse, it becomes pretty damn awesome. 
• Dire Puma^Sand: I can only conclude that someone messed up and meant this to be a much lower level choice.  There are core-only lower level choices that are superior.
• Dire Snake^MM2: Sigh.  Ok, if you really, really want a snake, this is the one to choose.  It poisons and constricts and is faster than most of it's brethren.  It's still bad, but not as bad as the rest.
• Smilodon (Saber-Toothed Tiger)^Frost: Comparable to the tiger/dire lion, the smilodon has the better burst damage, but the tiger wins out if combat goes for more than a round.
• Dire Tortoise^Sand: Trampler, unlikely-but-effective scout and mount. This is the ideal defensive choice at this level, with plenty of HP and AC.  But none of that is why you want this guy - it's for his automatic surprise round every encounter.  For a mostly outdoor campaign, this guy is one of the very best options.  (he's a leetle too big to go dungeon crawling without some serious work on your part ) Huge.
• Cave Triceratops^MH: It's Powerful Charge ability makes its one attack pretty threatening, and its trample attack isn't bad, but it's pretty mediocre all things considered.
• Cave Tyrannosaurus^MH: Wins some points for style, but the stats are really weak.
• Dire Vulture^Sand: Seriously, who was in charge of picking levels for the Sandstorm companions?  Dire Puma, Dire Tortoise and Dire Vulture are all in a row in the book, and it would take an idiot to think that the vulture or puma were even close to being a 10th level pet.  Anyway, the vulture is terrible.  Really, really terrible.
• Horrid Wolf^ECS: Like the horrid boar, one attack without anything else interesting to back it up just doesn't cut it.
• Horrid Wolverine^ECS: again, the dire wolverine is just too weak to for this template to save.

Level 13

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Core
   

• Dire Bear: Grappler and just generally mean brute. Best of all, it has a much better than average Will save. Large.
• Elephant: Decent damage + trample, but inferior to a lot of other choices.

Non-Core
   

• Ankylosaurus^MM2: Decent HP and AC (though nothing compared to the Dire Tortoise), but only one relatively weak attack.
• Diprotodon^Sand: Low HP, low AC, low damage = loser companion.
• Dire Elk^MM2: Like the elephant, but slightly weaker in every way except for saves.  (also, no trample)
• Fhorge^FF: Only one really weak attack, and only average stats in other areas.  Just say no.
• Horrid Lion^ECS: Excellent damage, though it's low BAB does hurt a bit.  A solid choice, regardless.
• Giant Banded Lizard^Sand: Grappler and general combatant with poison, possible mount. Huge.

Level 16

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Core
   

• Dire Tiger: Pouncer, with good feats and a lot of damage potential. Large.
• Triceratops: Charger - does decent damage on its first attack, but requires the "triceratops shuffle" to do sustained damage. (charge in, trample, move away as part of the trample, charge back in, etc).  Not my favorite, but it's functional if you always fight in areas with lots of room.
• Tyrannosaurus Dinosaur: Grappler and very stylish mount. Only one attack, but it hits decently hard. Huge.

Non-Core
   

• Dire Polar Bear^Frost: A better grappler than the tyrannosaurus, with better damage potential.  An all-around all star.
• Horrid Bear^ECS: If huge animals are a no-no, this guy is comparable to the dire polar bear - it doesn't grapple as well, but it does a lot more damage thanks to the Improved Natural Attack feat on all its attacks and the 3d6 acid damage added to both claw attacks.  Large.
• Dire Elephant^Sand/MM2: An enormous HP pool and decent trample damage.  Put a howdah on top and attack Minas Tirith.  Gargantuan.
• Horrid Elk^ECS: Only one primary attack to get the acid damage, and generally lower stats than the horrid bear.  Not a bad choice all things considered, but either of the bears are better.
• Dire Hippopotamus^Sand: A decent grappler, but inferior to most of the other choices this level.
• Indricothere^FF: Unimpressive stats all around.  Nothing terrible, but you can do so much better.
• Woolly Mammoth^Frost: Nope.  Nothing to see here.
• Mastadon^MM3: Almost identical to the woolly mammoth.
• Grizzly Mastadon^MM2: and now for entry #3 of our "almost identical prehistorical elephants"... bleh.
• Megatherium^FF: For a giant sloth, this thing is pretty quick   A nice AC, decent HP (though both worse than the dire tortoise), but it's Pin move is what makes it stand out.  Not a great companion, but it's workable.
• Quetzacoatlus^MM2: A Huge flying mount with Swallow Whole.  Since Swallow Whole is terrible, and you can get Roc if you need a flying mount for the party, give this guy a pass.
• Dire Rhinoceros^FF: Similar to the triceratops, except without Powerful Charge.  Much better other feats though; it really too bad =/
• Roc^Sand/MM: Flying mount for the entire party, replaces Horrid Bat (assuming size isn't an issue). Gargantuan.

Level 19

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• Horrid Elephant^ECS: Trampler, replaces Dire Elephant. Gargantuan.
• Horrid Rhinoceros^ECS: Sigh.  This would be an interesting choice if it actually had Powerful Charge.
• Horrid Tiger^ECS: It does a lot of damage, but ends up being inferior to some other choices due to already having Improved Natural Attack on its weapons.  Still a strong choice though.

[/list]

Further Companion optimization
First of all, if you're playing in a very High-Op game, go ahead and grab the Fleshraker, toss venomfire on it, and don't look back.  The combination is too incredible not to take if that's the direction your group is going. 

Now with that out of the way, let's look at some of the more generally applicable tips.

Get some barding!  Even if they're not trained for it, getting your companion some barding with no Armor Check Penalty is a relatively cheap and easy way to increase it's survivability.  And remember, just because you can't wear metal armor, there's nothing that extends that restriction to your companion.  And a set of +1 magic armor lets you attach armor crystals from MiC, and other goodies. 

The Warbeast Template from MM2 should also be available if you have a decent amount of downtime between adventures.  It's an awesome template: +3 Str, +3 Con, +2 Wis, +1HD, +10 Move, armor proficiency, plus a few other minor benefits.  In fact, it's so good that I've never had a DM that actually allowed it in-game   Best of luck to you on that, though!

Magebred/Horrid template: while it's never explicitly stated, it's implied in the ECS that the Horrid template can be applied to any dire animal at a -3 level adjustment.  If so, it opens up a lot of cool choices.  The two main things to look for are animals with 1. multiple primary attacks 2. high HD for the level.  There are a ton of benefits to this template, and I highly recommend it.  Magebred is trickier - on one hand, ECS flat out says "No Magebred Animal Companions", but then 5N comes out and explicitly gives us magebred bears and tigers.  Talk to your DM and find out how they rule it, and if you can get magebred, it's an awesome addition as well. 

For those more serious about getting better companions, there are some more options to consider:
Feats:

Aerenal Beastkeeper^RoEb: At first glance, this feat seems pretty cool; adds baboon to your list of allowed companions and treats it as +3 levels.  Except, the baboon is really terrible, so sadly this option is a waste.
Exalted Companion^BoED: this feat expands your companion list a bit, and more to the point, lets you get an animal with the celestial template.  The DR, SR, and energy resistance are nice, but what really makes the template worthwhile is the bump up to 3 Int.  At 3 Int, your companion has actual intelligence and doesn't need to worry about tricks or anything like that.

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Variable Level
Celestial Template added to any animal at an additional -1 level (so a -3 (4th level) becomes a -4 (5th level) option).  As mentioned, a solid option. 
Level 7
Asperi^MM2 - a cool mount with some interesting tricks.  Not a particularly powerful or versatile option though.
Giant Eagle/Giant Owl - the high intelligence is nice, and they do make good flying mounts, but they hardly seem worth a feat.

Wild Cohort^Web:  A second, slightly weaker companion for the cost of one feat isn't a bad trade.

Natural Bond^CAdv: to echo what I said above, a liberal reading of this feat could potentially give you and extra 3 effective levels to your companion progression.  Unlikely to fly unless your DM is familiar with Char-Op though.

A 1 level Beastmaster^CAdv dip: you trade one level of spellcasting and wild shape progression for +3 to your effective level for animal companion.  Let me make it clear - this is a bad tradeoff from an overall optimizing point of view!  However, if you have a concept that wants to rely on the companion as much as possible, it's not the end of the world.  No more than one level though!  The rest of the abilities are rubbish. 
[/list]

[Mooncrow]

Wild Shape
And now, the third part of the Triad of Power - Wild Shape.  Powerful forms come from almost every supplement, and with so many different forms available, take advantage of the opportunity to specialize!

Grappler
A specialty of the various varieties of bear and squid, and one of the most powerful Wild Shape strategies, as it maximizes your strengths (high Str, large size) while minimizing your weaknesses (generally poor AC). These forms are generally some of your best pure combat forms, whether or not you decide to actually grapple.

All of these forms have Improved Grab, and most of them have high strength, large size, and/or Abilities like Constrict and Swallow Whole.  Swallow Whole is a double-edged sword: yes, you're damaging the victim and keeping it from harming your friends or casting spells, but it can attack your very, very low gullet AC and do nasty damage. (If you get a chance to Swallow something with no light slashing/piercing weapon or natural attacks, go for it.) And never, ever, ever eat anything immune to acid. (Grapple checks, where noted below, don't include BAB. Just add your BAB to the grapple number listed below to get your grapple check total when in that form.)

Charger
Bipedal dinosaurs and big cats specialize in charging into battle and dealing as much damage as possible as fast as possible. The best forms usually have pounce and rakes, but a few forms with a single powerful natural attack and the powerful charge ability are also worth using.

Not many charger forms are bolded as recommended; this is mostly because charger forms are a matter of taste. Big cats dabble in grappling and can only bring their rakes to bear when charging or grappling, bipedal pouncer dinosaurs hit slightly harder and don't grapple, triceratopses have the Triceratops Shuffle, and rhinos have one powerful gore that does double damage on a charge. If you use big cats and bipedal dinosaurs often enough, you may want Multiattack, and if you use horned chargers often enough, you may want Power Attack.

Trampler
A specialty of elephants, herbivorous dinosaurs, and Treants. Most tramplers are Large- or Huge-sized, and have a high-damage attack or two. Trampling is great for taking out mooks (including swarms!), but most of the tramplers can also do a decent job of slugging it out with individual larger enemies. When buffing, remember that increased Strength ups the save DC for your trample as well as your damage.

Defensive
Sometimes you just need to avoid or shrug off attacks. Maybe you're focusing on spellcasting, or maybe you just want to get away. These forms have high AC, sometimes paired with defensive abilities (which will need to technically be "Special Attacks", due to the limitations of Wild Shape).

Aerial
Besides the obvious long-distance travel and scouting uses, druids who favor using their spells for offense will spend most of their time in aerial forms, not just because of the maneuverability but because of the high Dex for touch attacks, AC, and initiative checks. (Contrast this with grappling forms, where combat spellcasting is usually confined to buffs before or at the beginning of a fight.) Generally, they aren't as good in melee as the land- or water-bound alternatives, but maneuverability does come at a price.

Aquatic
Sometimes, you're going to have to spend some time in the water. Forms with this notation have swim speeds and unless noted otherwise, can breathe underwater.

Tool-User
Medium-sized, more-or-less-human-shaped forms which can use your equipment normally instead of having it meld into your Wild Shape form. This is a hideously powerful strategy at high levels, but you need to drop all your stuff and pick it up again, meaning you'll need a long Wild Shape duration as well as time to prepare. (Many GMs will house-rule this controversial rule; see more below in the Controversial Options section.)

Level 5
 

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• Baboon - Tool User - Str 15 Dex 14 AC 13 - It probably has better stats than your physical stats, and it has natural armor and a bite attack. All in all, not too bad.
• Crocodile - Grappler: check +4 - The grappler form of choice if Fleshraker is out of the question. Hard-hitting enough to be useful even outside of a grapple.  Swim speed, but doesn't breathe water.
• Fleshraker Dinosaur^MM3 - Charger, Grappler*: check +3 An absolutely OMG form, if it's allowed. Fleshrakers can charge, pounce, trip, pin, and poison, all in one round, and also has great AC to boot. It remains awesome whenever you have to charge something, especially if it's medium-sized or smaller.  Certainly the most powerful choice for a long while.  (and if you use venomfire - holy crap, 3 poison attacks/round)
• Deinonychus Dinosaur: Charger -  Nothing can compare to Fleshraker, but this is fine in a fight on its own merits.
• Leopard: Charger - The core-only and no-dinosaur alternative to the Fleshraker and Deinonychus.
• Protoceratops Dinosaur^Sand: Charger - A bit tougher and harder-hitting than Deinonychus, but not as good when it comes to stand toe-to-toe, and definitely not as good as the Fleshraker.
• Desmodu Hunting Bat^MM2 - Defensive: AC 20, Aerial: Speed 60'(good) - Your starter defensive form, with AC 20 and touch AC of 17. It's decent flight speed is just gravy. 
• Dire Hawk^RotW - Aerial: Speed 80 ft. (average) - Faster than Desmodu Hunting Bat, but has slightly lower Dex and AC, and isn't as hard-hitting.
• Eagle - Aerial: Speed 80'(average) - The best core-only flier at this level, but has mediocre AC and Dex, and abysmal attacks.
• Squid: Aquatic: Swim 60'  Grappler: check +6. Not as strong as crocodile, but has more attacks and breathes water.
• Medium Shark - Aquatic: Swim 60' -  Fast swimmer, decent biter.
• Dog, Riding Dog, Donkey, Pony - Spy - Forms to snoop around town.
• Swindlespitter Dinosaur^MM3 - Utility - AOE blinding poison attack (combine it with Venomfire from Serpent Kingdoms!), and may double as a spy form in certain areas. (MM3 says some cultures consider Swindlespitters to be sacred.)

Level 8
   

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• Brown/Polar Bear: Grappler: check +12 - The quintessential grappler form, with strong attacks, fair AC, and a great grapple check. The bears are versatile enough to fight a crowd, then grab a tough foe and tear it apart in a grapple. (Choose Polar if you want to min-max every tiny bit; the two are identical with regard to Wild Shape save for the Polar Bear's swim speed.)
• Dire Lion: Charger, Grappler: check +11 - If the Fleshraker isn't available, this is an interesting compromise between first-strike-charger forms and slugger/grappler forms like the Polar Bear. It isn't as hard-hitting as most traditional grappler forms, though.
• Cave Triceratops^MiniHB: Charger, Trampler: Large, 3d6+6 DC 18 - The first form where you can try the Triceratops Shuffle. Charge a foe (doing double damage because of Powerful Charge), then Trample that foe and move away as part of the Trample move. Then charge again, and repeat. This isn't the best charger or trampler, but the combination is killer.
• Desmodu Guard Bat^MM2 - Aerial: Speed 60'(good) - Exactly like Dire Bat, only faster. A balanced flier form.
• Dire Bat - Aerial: Speed 40' (good) - A typical aerial form, with good AC, good Dex, and a single, mediocre attack. Inferior to the non-core options.
• Dire Eagle^RoS - Aerial: Speed 60'(average) - Very strong for a flier, able to attack somewhat effectively or carry a party member or two. Compared to the other fliers, its AC and Dex aren't very good, but they're passable.
• Giant Octopus - Grappler: check +9, Aquatic: Swim 30' - Not as strong as polar bear, but has nine(!) attacks, Constrict, and water breathing.
• Large Shark - Aquatic: Swim 60' - Speedy swimmer, but not terribly handy in a fight compared to the alternatives.
• Megaraptor Dinosaur^{MM errata} - Charger - This is harder-hitting than Dire Lion and doesn't rely on Rakes to deal damage (and is thus better in a toe-to-toe fight), but it doesn't grapple. Use it for charging and fighting foes you couldn't grapple anyway.
• Rhinoceros - Charger - WHAM. One big nasty hit, especially when charging but even in a toe-to-toe fight.
• Cave Anklyosaurus^MiniHB - Defensive, Trampler: Large, 3d6+7, DC 18 - Awesome AC (24) and its single attack is still quite effective, when trampling isn't practical.

Level 9
   

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• Cave Tyrannosaurus^MiniHB - Grappler: check +11 - Not quite as hardhitting as Polar Bear, but this is your first form with Swallow Whole (which only works on Small or smaller foes, mind).
• Smilodon(Sabre-Toothed Tiger)^Frost - Charger, Grappler: check +11 - A marginal improvement on Dire Lion: x3 critical on bite, best attack is primary, claw attacks can start grapple.
• Diprotodon Dinosaur^Sand - Trampler : Large, 2d6+12, DC 22 - It tramples, doing a better job than the Cave Dinosaurs. Other than that, it's fairly unremarkable, besides the pathetically low AC.

Level 12
   

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• Desmodu War Bat^MM2 - Aerial: Speed 40'(good) - A fairly hard-hitting attacker, large enough to carry party members. Only slightly less evasive than Legendary Eagle, but physically much stronger.
• Dire Bear - Grappler: check +14 - Like the Polar Bear, only moreso.
• Ironthorn^Sand - Defensive: AC 24 - A massively tough form, and has ridiculously high-DC paralytic poison (along with decent reach and some mediocre grappling ability). Too slow to stay in this form all the time, though. Plant.
• Legendary Eagle^MM2 - Defensive: AC 25, Aerial: Speed 100'(average) - A very evasive form, with a ridiculous touch AC of 21. Doesn't hurt at all that it's a fast flier.
• Vine Horror^FF - Tool User - Str 18 Dex 10 AC 18 - Inferior to Legendary Ape (except in that it can talk), but Vine Horrors are naturally intelligent and tool-using, so a strict GM may be more lenient. (Plus, spiffy plant-type immunities.) Useless at this level except as a tool-user. Plant.
• Warhound Impaler (Lesser Battlebriar)^MM3 - Grappler: check +10, Trampler: Large, d8+9, DC 22  - This isn't the hardest-hitting or strongest grappler, but it can impale (Medium-sized or smaller) grappled foes on its thorns with a free-action grapple check, rendering them helpless. Not pinned, not grappled, but helpless. Plus, it has an AOE attack and tramples! Plant.

Level 13
     

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• Legendary Ape^MM2 - Tool User - Str 30 Dex 17 AC 19 - Massively strong and surprisingly tough, and has a full set of powerful natural attacks to go with any weapons you might have. It's still useful without the item-melding rule, because of high Str, powerful attacks, and rend.

Level 14
   

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• Legendary Wolf^MM2 - Defensive - AC 24 - A well-rounded defensive form, but not strong or large enough to be an impressive tripper or even much of a melee combatant.

Level 15
 

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• Dire Tortoise^Sand - Defensive, Trampler: Huge, 4d8+12, DC 25 - Respectable trample damage, great AC (25), and it always gets a surprise round. An OMG form.
• Dragonhawk^5N - Aerial: Speed 120'(average) - A hard-hitting and fast flying form, large enough to carry your allies. Not as agile as Legendary Eagle, though. It has Blindsense you can pick up with Enhance Wild Shape, as well.
• Elephant - Trampler: Huge, 2d8+15, DC 25 - The first core trampler you'll get access to, but it's inferior to the non-core alteratives.
• Giant Banded Lizard^Sand - Grappler: check +17 - Comparable to the Dire Bear in damage output, but has better grapple check and poisoned claws. It has terrible AC, though.
• Giant Squid - Grappler: check +20, Aquatic: Speed 80' - Hard-hitting and awesome in a grapple. One of the best aquatic forms period.
• Grizzly Mastodon^MM2 - Trampler: Huge, 4d8+18, DC 29 - A massively hard-hitting trampler, either in a trample or a melee. It isn't as tough as the Dire Tortoise, though.
• Ironmaw^FF - Defensive: AC 25, Grappler: check: +N/A - This isn't strictly a grappler, but it fights like one. Ironmaws have six tendrils with ridiculous reach, and a tendril hit can attach to a foe, pulling them within reach of the Ironmaw's so-so bite or OMG Engulf ability, which does fair damage and suffocates. Tendril hits also cause bleeding and Con damage. Did I mention the Ironmaw has great AC? The only drawback is the exceedingly low speed, which keeps you from staying in Ironmaw form all day. Plant.
• Octopus Tree^FF - Grappler: check: +28, Aquatic: 50' - Eight(!) Improved Grab attacks, Swallow Whole, great damage, and frightful presence. A top-tier grappler form. Too slow on land to spend all your time in this form outside of an aquatic campaign, and it isn't clear if it breathes water or air. Plant.
• Saguaro Sentinel^Sand - Defensive: AC 22 Trampler: Huge, 3d6+16, DC 27 - A compromise between Grizzly Mastodon (it's almost as strong) and Dire Tortoise (it's almost as tough). It doesn't trample as well as either, though. As a nice little bonus, though, it talks. Plant.
• Tendriculos - Grappler: check +17 - The ultimate Swallower. Anything that can't make the DC 20 Fort save before cutting its way out will die. Plant.
• Treant - Defensive: AC 20, Utility, Trampler: Huge 2d6 +13 DC 22 - Plant immunities, decent AC, rounded out with decent attacks and okay trample. It's not great at one thing and there are non-core forms that eclipse it, but it's a versatile mid-level form.  Treants also do double damage against objects. Plus, it talks! Plant.

Level 16
 

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• Dire Tiger - Charger - An incremental improvement on Smilodon and Dire Lion, and good for the same reasons.
• Triceratops Dinosaur - Charger, Trampler: Huge, 2d12+15, DC 28.  The real deal when it comes to the Triceratops Shuffle. Charge, trample and move away, charge, trample and move away, repeat until dead. If you've got Power Attack, you're going to want to use it.

Level 18
 

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• Dire Polar Bear^Frost - Grappler: check +22, Aquatic: Swim 20' - The ultimate grappler form, and the highest strength you can get.
• Legendary Horse^MM2 - Spy - One of the very few spy forms with some combat ability.
• Tyrannosaurus Dinosaur - Grappler: check +17 - The core-only alternative to the Dire Polar Bear or Giant Banded Lizard. Isn't as tough or hard-hitting, but it's a heck of a lot more stylish, and it does have Swallow Whole.

Misc.
Everything else. They may have useful or unusual in- or out-of-combat abilities, or otherwise deserve special mention.

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Level 8
 

• Dire Wolf - Has the strength and size to actually use trip ability, in those situations where tripping is possible but grappling isn't feasible. AC is fairly low, however.
• Valenar Riding Horse^ECS - Long distance travel form, with its 80 ft. land speed. Plus, you can carry a party member.

Level 12
   

• Myconid Sovereign^MM2 - The Sovereign has a range of spell-likes that aren't really spell-likes. Handy ones you can use include telepathy spores, animate dead spores, and pacifying spores.

Level 15
   

• Yellow Musk Creeper^FF - The Yellow Musk Creeper's Mind Puff ability makes enemies helpless at range. Plus, you can eat your opponent's brain, and then as long as you stay in that form, they will serve you until they die in two months.

To do list:
Abberations, Vermin, Exalted
Still quite a bit of work to do in this section; some of the stats are off, and I still need rate them.

[Mooncrow]

Equipment

Armor
There are a couple different ways you can go with druid armor - you can either go the dragonhide or ironwood route, and enchant them with the "wild" property, or just grab a monk's belt (or robe if you have access to Pathfinder gear) and a wilding clasp.  For more fun , buy your wizard a wand of mage armor and have him cast it on you prior to going into battle.  Personally, I prefer the second option; yes you miss out on a few nifty armor options, but the +3 for wild so that it can be useful all the time is just painful.

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Types:
Dragonhide Breastplate - this is a decent base armor until you can afford a monk's belt. 

Enhancements
Fortification (DMG +1, 3, 5) - Negate some or all of critical and precision damage
Ghost Ward (MIC +1) - add your armor enhancement bonuses to touch AC - very, very handy.
Soulfire (BoED +4) - Immunity to death effects, energy drain, and all negative energy effects
Death Ward (MIC +1) - once per day, ignore a death effect
Energy Immunity (MIC +2) - once per day, gain immunity to an energy of your choice for 1 minute
Crystals
Restful Crystal (MIC 500g) - sleep in your armor with no penalty

Shields

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Types:
Masterwork Darkwood Heavy Wooden Shield
Shield Spike +1 (obviously, not a metal one) - makes a great enchantment platform for enhancements that you always want on.
Enhancements
Animated (DMG +2): the single best enhancement you can get, now your shield is usable no matter what form you swap to.
Fortification (DMG +1, +3, +5): Just like on armor, probably better on the shield, since armor has a wider choice of other abilities.
Ghost Ward (MIC +1): Again, just like the armor version; and together you can add up to +10 to touch AC
Wand Chamber (Dungeonscape 100g) - useful to have a wand at hand if it's needed.
Crystals
Arrow Deflection (MIC 500-5000g) - up to a +5 deflection bonus against ranged weapon attacks.  Would be nice if it worked against ranged touch attacks too, but at 10% of the cost of a Ring of Protection, it's hard to argue.

Weapons

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Types
Quarterstaff - your melee weapon of choice at early levels, and for out of wild shape moments at high levels (or if you're in a tool using form) You might as well embrace it, since once you have access to 6th level spells for spellstaff, it would replace any other choice anyway^^
Ironwood Spiked Gauntlets +1 - makes a great enchantment platform for enhancements that you always want on.
Enhancements
Warning (MIC +1) - a +5 insight bonus to initiative?  Yes, please.  Perfect to go on your gauntlets.
Sure Striking (PGtF +1) - really good for the cost
Smoking (LoD +1) grants concealment.
Crystals
Return, Least and Lesser (MIC 300, 1000g) Now, one interesting thing about rods is that they are usually considered weapons, so you can attach these crystals, store your Metamagic rods in a Quiver of Ehlonna and then draw them as a free action. 

Arms

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Bracers of Lightning (MIC 11,000g) - add 1d6 to all your melee and ranged attacks at the cost of a swift action every round - usable in wild shape. 
Bracers of Repulsion (MIC 4000g) - 3/day as a swift action, push all enemies within 10 ft back 5 feet.  Good for creating some breathing room.
Armband of elusive action (MIC 800g) - 1/day avoid 1 AoO

Body

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Robe of Thunder (MIC 38,000g) - melee attackers take 2d6 sonic damage - also effectively grants evasion against sonic attacks.  Usable in wild shape.
Robe of mysterious conjuration (MIC 10,000g) - 3/day spontaneously cast Summon Monster by sacrificing a spell slot of the appropriate level
Robe of Eyes (DMG 120,000g) - constant see invisible, darkvision 120 ft, +10 Spot and Search, can't be flanked and retains Dex bonus even when flat-footed.  Expensive, but potentially useful.

Face

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Third Eye Clarity (MIC 3000g) - 1/day immediate stun/daze/confuse/fascinate negation - for the price, incredibly good at low-mid levels. 
Mask of the Tiger (MIC 4000g) - low-light vision for races that don't have it.
Blindfold of true darkness (MIC 9000g) - 30ft blindsight
Hathran Mask of True Seeing (UE 75,000g) - Continuous True Seeing
Third Eye Conceal (MIC 120,000g) - Continuous Mind Blank

Feet

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Anklet of Translocation (MIC 1400g) - 2/day teleport 10' as a swift action
Quicksilver Boots (MIC 3500g) 2/day take your move speed as a swift action

Hands

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Gauntlets - as mentioned above, a good enchantment target
Glove of the Master Strategist(Ghost, 3600g) - like Gloves of Storing, only cheaper and allows you to cast True Strike 1/day
 

Head

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Circlet of Mages (MIC 5000g) - functions like a multi-use pearl of power, only more flexible. Retain up to 3 1st level spells, 1 1st and 1 2nd, or 1 3rd level spell. 
Circlet of Persuasion (DMG 4500g) - useful if you do much with Handle Animal, or are the party face.

Rings

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Ring of Freedom of Movement (DMG 40,000g) - yes, you can cast the spell, but this completely shuts down attempts to grapple you, along with many other nasty effects - it's worth having it all the time.
Ring of Blinking (DMG 27,000) - Blinking at will, lots of uses for this
Ring of Mighty Summons (CM 14,000g) -   3/day, your summons can have max hit points, but half duration; great for summoner builds
Ring of the Beast (CC 8,000g) - treat all of your SNA spells, except for the highest you can cast, as if they were the next rank (SNA III is cast as if it were SNA IV, for example) - great way to make your lower level spell slots more powerful.
This is also a great slot for custom items

Shoulders

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Mantle of the Beast (CC 18,000g) - wild shape as a swift action, and all natural attacks gain a +1 enhancement bonus to attack and damage. 
Scry Shroud (MIC 4000g)  +5 on saves against divinations; if you detect scrying sensor, become invisible for 10 rounds.  Useful if your DM starts the divination war at lower levels.
Cloak of Resistance (DMG 1000-25,000) - mildly useful until you get Greater and Superior Resistance
Cloak of Displacement, minor (DMG 24,000) - Continuous 20% miss chance
Cloak of Charisma (DMG 4000-36,000) - go ahead and remake this one according to MIC rules

Throat

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Wild Shape Amulet (MoF 40,000) - increases your level for wild shape by 4
Chronocharm of the Horizon Walker (MIC 500g) - 1/day move half your move speed as a swift action.  Great for the cost at low levels
Chronocharm of the Uncaring Archmage (MIC 500g) - 1/day cast as spell of 3rd level or lower as if it had Rapid Spell applied.
Reliquary Holy Symbol (MIC 1000g) - Nice if you're going the Wild Reaper variant with DMM
Ankh of Ascension (MIC 9000g) - +4 caster level 3/day
Amulet of Health/Periapt of Wisdom (DMG) - like most of the stat boosters - make new versions with the MIC rules

Torso

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Bolt Shirt (MIC 5000g) - 1/day teleport 60' as a move action, not that great, but probably the best shirt item available
Tunic of Steady Spellcasting (MIC 2500) +5 to concentration checks

Waist

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Monk's Belt (DMG 13,000) - gain your wisdom bonus as an AC bonus
Belt of Battle (MIC 12,000g) - +2 initiative and daily charges that you can spend for extra actions; so good.
Healing Belt (MIC 750g) - daily charged item of healing, super cheap and frees up those couple spell slots for something actually useful
Belt of the Wide Earth (MIC 8000g) - 2/day can burn a 5th level spell slot to teleport - very very handy for a druid, with teleport options being so limited.

Relic

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Other

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Wilding Clasp (MIC 4000g) - probably the most useful item in the game for druids - keep your magical items active while in wild shape
Pearl of Speech (MIC 600) - absolutely essential; place it in your mouth and you can speak one language, allowing you to speak while wild shaped
Pearls of Power (DMG 1000-81,000g) - more spells?  Oh my, yes.
Metamagic Rods - I have a huge love for these, as mentioned above, I put them in a Quiver of Ehlonna so I have speedy access.
- Extend - Lesser Extend should probably be your first rod, keep your buffs going and make your summons worth using.  Still good even at higher levels.
- Quicken - expensive as heck, but really, really great.
- Rapid* - has to be a custom item, sadly, but for summoners, this is really great.
- Twin* - another custom item, should be the same cost as Quicken - ie. crazy expensive - probably not worth it unless you're playing with higher WBL than normal.
- Chain - situational, but decent.
Heward's Handy Haversack (DMG 2200g) - never leave home without it; the best of the general use dimensional bags.
Heward's Fortifying Bedroll (CM 3000g)
Metamagic Wandgrip (CM 6000g) - if you like using wands, this tends to make them a lot better. 
Summoner's Totem (MIC 3100g) - Like Imbue Summoning, but no level adjustment, and works on any level summon.
Strand of Prayer Beads (DMG 25,800g) - the Bead of Karma is the interesting one, +4 CL for 10 minutes a day.  For the cost, you might as well get the full strand, and get slotless healing and blasting along with it.
Tomes and Manuals - Save up for the +5
Special Holy Symbols (CC 350g) - depending on your deity, you can gain various benefits, usually increased CL for certain types of spells.  Almost certainly worth it. 

Magic/Legendary Locations

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Otyugh Hole (CS) - Iron Will is the best of the bonus feats; useful for getting a couple of the prestige classes without wasting a precious feat slot.
Worldmeet Glade (CM) - convince your DM to allow it to apply to non-arcane spellcasters  

[Mooncrow]

Venerable Dragonwrought Kobolds
There have been several suggestions that Venerable Dragonwrought Kobolds are "teh ub4r" and need to take the top spot as far as optimized races go.  As a practitioner of practical optimization, this is a bit more juice than we need to squeeze out for most campaigns.  Games that involve not just high-level, but theoretical optimization will lend themselves better to +9 mental stat boosts for a feat.  Furthermore, any class that benefits from high mental stats can benefit from being a VDK, so it isn't a Druid-specific optimization either.

With that said, if your campaign demands nitrous just to keep the game moving or you are dying to play an ancient kobold shaman, by all means do so.  But don't expect to change this author's mind about the Druid-specific utility of the VDK.

Prestige Classes

Moonspeaker
Arcane Hierophant
Planar Shepherd
Fochluchan Lyricist

[Mooncrow]

Reserved

Last reserve - feel free to post.

There's still a lot of formatting and cleaning up to do, but all of the info is over here now.

Current project:  a complete list of Animal Companions and their rating. 

[cru]

The Aberration Wild Shape feat from Lords of Madness allows a druid to wild shape into an aberration. According to an article on the WotC site, in Eberron, the Aberrant Dragonmark feat can be used instead as a prerequisite for this feat.

Aberration forms have a wild array of special attacks. Some of the most interesting forms are listed below:

Name+Reference	Size	HD	AC	Stats	Attacks	Misc
Tentacle Spider (SoX)	medium	3	16	11/17/14	4x touch +4 (dex poison) + bite	Ranged entangle
Fiery Sandhog	medium	4	17	15/12/12	4 bite +5 melee and 2 claws +0	burrow, climb
Tako (OA)	medium	4	17	20/15/12	8 attacks	Aquatic, Improved Grab, Constrict
Dustblight (Sand)	medium	5	20	20/17/12	Bite +8 (1d8+5), 2 claws +6 (1d3+2)	Burrow 30 ft.
Rust Monster (MM)	medium	5	18	10/17/13	corroding touch attack, weak bite	Corrode metal
Dolghast (MoE)	medium	6	17	19/14/13	2 claws +8 (1d6+4), bite +3 (1d6+2)	Con damage
Vivisector (MM5)	medium	7	21	15/18/14	2 claws +8 melee (1d8+2), sting +4	Poison DC15 1d6/1d6 str, fly
Cloaker (MM)	large	8	19	21/16/17	Tail +8 (1d6+5), bite +3 (1d4+2)	Fly 40 ft., Moan, Engulf
Ineffable Horror (Und)	large	5	18	19/13/16	2 slams +7 (1d4+4)	Fly 60 good, grappler with con drain
Mimic (MM)	large	7	15	19/12/17	2 slams +9 (1d8+4)	Adhesive, Crush
Rukanyr (FF)	large	7	22	21/7/24	10 attacks	poison, stunning attack, climb
Squamous Spewer (Drac)	large	8	22	19/13/17	6 bites +10 (1d10+4)	Roar (fear)
Dharculus (PlH)	medium	8	22+	12/14/20	6 tentacles +8 (1d4+1)	Improved grab, ethereal bite
Otyugh, Lifeleech (mm3)	large	9	21	27/16/23	4 tentacles +14 (1d8+8) and bite	Constrict, improved grab
Stone Singer (mm3)	large	9	21	20/10/18	Bite +10 and 6 claws +8	DC 18, 1d4 Dex/1d4 Dex
Hook Horror (mm2)	large	10	22	24/17/14	2 claws +13, bite +8	Improved grab, power sunder, rending bite
Chuul (mm)	large	11	22	20/16/18	2 claws +12 (2d6+5)	Improved grab, constrict, paralysis, aquatic
Darktentacles (MM2)	large	9	18	19/15/17	12 slams or 12 weapons	Improved grab, Constrict, 15 ft reach, swim
Death Kiss Beholderkin (MoF)	large	12	16	16/14/16	10 tentacles (1d4+3) @ 20 ft reach	Improved grab, Blood Drain
Chwidencha (DotU)	large	12	24	22/17/20	4 claws +15 (1d6+6), Pounce	Improved grab, climb/burrow
Ocularon (FF)	large	12	21	18/15/17	4 melee tendrils, 1 ranged touch	Improved grab, poison, steal eyes, death throes
Thoon Elder Brain (mm5)	large	12	26	26/14/30	8 tentacles +17 (1d6+8+2d6 acid)	Dual action (!), acid burn, fly
Urophion (LoM)	large	12	24	19/13/16	6 ranged touch, 1 bite	drag, extraction, strands
Delver (MM)	huge	15	24	27/13/21	2 slams (1d6+8+2d6)	Corrosive slime (vs stone and metal)
Athach (MM)	huge	14	17	26/13/21	with melee weapons + bite	Poison
Madcrafter of Thoon (mm5)	huge	10	20	30/12/26	Bite +16 (2d8+15+4d6 acid)
Five-headed Terror (mm3)	medium	15	21	13/18/15	5 bites +16 (1d6+1+poison), Pounce	venomfire target
Nagahydra (SK)	huge	18	20	30/14/20	7 bites (2d6+10+poison)	swim, poison 1d12 con
Moonbeast (MM2)	huge	18	17	30/15/21	10 rakes (4d6+10)	Constrict, improved grab, Bite
Chilblain (Frost)	large	20	35	28/17/24	tail and 4 claws	cold aura, frost touch
Maulgoth (FF)	huge	20	39	29/25/27	4 tentacles and bite	constrict, improved grab

[cru]

Ways to get access to vermin forms

Vermin Shape (ECS 62) feat
require: druid5, nongood, child of winter
benefit: lose access to animal forms, get access to vermin forms

Wild Shape (Waste Vermin) (Sandstorm 47)
10th level druid alternative class feature
lose one wild shape use per day, gain access to "waste" vermin forms

Vestment of Verminshape (DMG2 273)
20000 gp, get access to vermin forms, no strings attached

City-Shape (Cityscape web enhancement)
5th level druid alternative class feature
slower size progression (max. large), can shape to both animals and vermin; lose plant shape, gain swarm shape

Spider-Shape (DotU 58)
5th level druid alternative class feature
lose animal forms, gain monstrous spider forms (only the spiders from MM (?))

Vermin forms are generally weaker and less numerous than animal forms. Giving up animal forms is a very high price to pay and a flavor decision. Some notable forms are listed below:

Name	Size	HD	AC/touch	Abilities	Attacks	Misc
Giant Cockroach (Ud)	M	4	20/16	21/18/16	1 melee, stench (DC15 vs nausea)	40, climb
Giant Bee (SRD)	M	3	14/12	-	-	fly 80 good
Monstrous Crab (Storm)	M	3	16/10	15/11/12	2 melee, improved grab (+6), constrict 2d6+2	20
Dire Maggot (LiM)	S	6	19/13	13/15/12	1 melee+poison	40, climb
Lesser Knell Beetle (MM3)	M	6	20/11	18/12/18	3 melee, rend, trample (2d8+6/DC17), shake the earth	40, burrow
Giant Stag Beetle (SRD)	L	7	19/9	23/10/17	1 melee, trample 2d8+3/DC19	20
Sword Spider (MonoF)	L	5	17/9	18/10/14	9 melee, impalement, poison	20, climb
Spitting Spider (DotU)	L	7	18/12	22/17/18	3 melee; ranged touch (spit), dex poison, pounce	40, climb
Large Monstrous Crab (Storm)	L	6	18/9	21/11/12	2 melee, constrict, improved grab (+13)	20
Monstrous Crab	L	7	19/11	22/14/21	2 melee, constrict, improved grab (+14), powerful claws	40, swim
Giant Praying Mantis (SRD)	L	4	14/8	19/8/15	2 melee, improved grab (+8)	fly 40 poor
Giant Wasp (SRD)	L	5	14/10	18/12/14	1 melee+poison	fly 60 good
Monstrous Toebiter	L	10	18/10	26/13/20	3 melee, poison, improved grab (+12), blood drain	20, swim
Knell Beetle (MM3)	L	12	24/9	26/10/23	3 melee, rend, trample (4d6+12/DC24), shake the earth	50, burrow
Chelicera (MM3)	M	12	19/14	14/19/12	3 melee, improved grab, blood drain	30
Tangle Terror (DotU)	M	12	22/14	14/19/18	1 melee+poison; web 8/day, mad.webs (confusion)	30, climb
Leechwalker (MM2)	M	13	12/10	18/11/16	2 melee+wounding, improved grab (+4), blood drink	30, swim
Widowmaker (DotU)	L	13	24/12	20/17/22	1 melee+poison; improved grab (+9), blood drain	30, climb
Bonespear (FF)	L	15	27/12	22/17/19	3 melee, 2 ranged, poison, attach, drag, horns	40
Huge Monstrous Crab (Storm)	H	12	22/8	25/11/14	2 melee, constrict, improved grab (+19)	30

SRD vermin: http://www.d20srd.org/indexes/monsters.htm
Wizards monster list: http://www.wizards.com/default.asp?x=dnd/lists/monsters&tablefilter=vermin
searchable list: http://www.imarvintpa.com/dndLive/FindMonster.php

[cru]

Gargantuan wild shape (via Megalodon Empowerment)

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Megalodon Empowerment (Druid 8, Stormwrack) is a nice spell. Apart from other cool stuff (e.g. divine power for druids), it allows you to wild shape into animals one category larger than normally allowed.
List of all gargantuan animals I could find:
MM1 has 12 HD Whales (35 Str) and Roc (18 HD, 34 Str flyer).
MM2 has two 20 HD choices: Spinosaurus with Frightful Presence and Dire Elephant with 40 Strength.
Frostburn has a 15 HD Zeuglodon: fish, 38 Str and stunning tail attack (DC31 fort for 2d4 rounds).
SK has 18HD Stegosaurus, underwhelming.
Stormwrack has 16 HD Plesiosaur, aquatic, faster but weaker than Zeuglodon.

Non-core Summon Nature's Ally

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MM3 – storm elementals SNA3 – SNA8
MM5 – fetid fungus SNA2
FF – bloodthorn SNA4, dire rhino SNA7, fossergrim SNA5, kelp angler SNA7 (SLAs), kelpie SNA9, octopus tree SNA9, oread SNA6 (earth SLAs!), sporebat SNA8 (enervation), spriggan SNA4 (shatter), viper swarm SNA6, yellow musk creeper SNA4
Stormwrack – various aquatic creatures
PlH – elementite swarm

Prestige Class option:

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Holy Orders of the Stars (Dragonlance book) has the Wild Fury of Schilev on pg. 58.
You need to be able to cast Greater Magic Fang and have Endurance and Toughness.
It has 10/10 Casting, 10/10 Wildshape (Full), no AC, and you get a TON of class features.
Class Features include:
5 bonus feats from a good list. Ex: Natural Spell, Multiattack, Improved Natural Attack, Improved Critical...
+20' Speed while Wildshaped.
Constant Greater Magic Fang.

To be updated in OP:
riding dog: superior to wolf in every way except speed
updated spells: http://brilliantgameologists.com/boards/index.php?topic=1354.100

From wiki: http://coboard.wikia.com/wiki/Druid
-how to summon faster
-equipment?

How to qualify for druid PrC/Feats as a non-druid

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Shamelessly stolen from Lists of Stuff (http://forums.gleemax.com/showthread.php?t=662842) + added some more stuff

Wild Shape
Druid 5
Ranger variant 5 (UA)
Monk variant... Dragon???
Abolisher 1, ecl 7, Lords of Madness
Lion of Talisad 3, ecl 8, Book of Exalted Deeds
Moonspeaker 5, ecl 13, Races of Eberron
Landforged Walker 5, ecl 10, Eberron: Secrets of Xen'Drik - "plants shape", see text
Mulhorandi Divine Minion: http://www.wizards.com/default.asp?x=dnd/mb/20050209a
Shapeshifter (prestige class, OA, updated in Dragon 318)
Savage Vampires (Dragon mag 348)

Animal Companion
Druid 1
Ranger 4
Ranger 4 (elf racial substitution level), Races of the Wild, Elven Hound, advances as animal companion, see text
Peregrine Runner 1, ecl 8, Races of Stone, peregrine falcon only
Beastmaster 1, ecl 6, Complete Adventurer, also gains extra companions, see text
Musicless Bard - http://www.d20srd.org/srd/variant/classes/variantcharacterclasses.htm
Sorcerer/Wizard - http://www.d20srd.org/srd/variant/classes/variantcharacterclasses.htm
Wild Cohort feat - http://www.wizards.com/default.asp?x=dnd/re/20031118a

Wild Empathy
Druid 1
Druid 1, class variant, Dungeonscape, vermin empathy, replaces wild empathy
Ranger
Spirit Shaman 1, Complete Divine
Initiate of Nobanion, feat, Champions of Valor - only useable on felines
Animal Lord 1, ecl 6, Complete Adventurer
Beastmaster 1, ecl 6, Complete Adventurer
Chameleon 1, ecl 6, Races of Destiny, wild focus
Totemist 1, Magic of Incarnum
Totem Rager 1, ecl 7, Magic of Incarnum
Black Blood Hunter 2, ecl (8?), Player's Guide to Faerun
Primeval 1, ecl 9, Frostburn - specific animal only
Vandalis Beastkeeper 1, ecl 5, Eberron: Dragonmarked
Call of the Beast, least warlock invocation, Complete Mage, can also speak with animals
Natural World, mantle, Complete Psionic
Weretouched Master 2, ecl 7, Eberron Campaign Setting
Vermin Keeper 1, ecl 6, FR: Underdark, vermin only

Stacks
Scorpion Wraith, ecl 6, Eberron: Secrets of Xen'Drik, also treat vermin as magical beasts
Swanmay, ecl 6, Book of Exalted Deeds

Special Mention
Urban Savant 2, ecl 7, Cityscape, urban empathy

Trackless Step
Druid 3
Scout 3, Complete Adventurer
Wildrunner 1, ecl 6, Races of the Wild
Nightsong Infiltrator 3 (self), ecl 10, affects your team at level 7
Justice of Weald and Woe 4, ecl 10, FR: Champions of Ruin
Duraak'ash 5, ecl 10, Eberron: Dragonmarked
Bamboo Spirit Folk, race, Oriental Adventures
Holt Warden 3, ecl 8, Complete Champion

Special Mention
Druid or Scout 3, class variant, Cityscape Web Enhancement, "lay low", can't be found with urban tracking

Able to cast spell xxx
cleric with access to plant or other domain can sometimes qualify
dragon with "child of eberron" learns druidic and casts spells from the druid spell list as arcane spells

Notable plant forms:
Thunderspiker
Night Twist (MM3)
Elder Viper Tree (Expedition to Demonweb Pits)

[gorfnab]

Other Druid Variants
Metal Master - Drg #311
Sidhe Scholar - Drg #339
Storm - Drg #328
Urban - Drg #317
Totem - Drg #335
Wind Walker - Drg #311
Winter Warden - Drg #311
Focused Animal - Drg #347
Environmental (Druid weapon list) - Drg #331

[nijineko]

thank you for this thread.

as a side note, but related: would you be interested in mentioning methods of qualifying for druid prestige classes without using druid at all? the bear warrior and the shapechanger (OA 3.0 prestige, updated to 3.5 in dragon 318) both of which grant wildshaping specifically, without requiring it as a prerequisite.

[Bastian]

Wild Shape
Druid 5
Ranger variant 5 (UA)
Monk variant... Dragon???
Abolisher 1, ecl 7, Lords of Madness
Lion of Talisad 3, ecl 8, Book of Exalted Deeds
Moonspeaker 5, ecl 13, Races of Eberron
Landforged Walker 5, ecl 10, Eberron: Secrets of Xen'Drik - "plants shape", see text
Mulhorandi Divine Minion: http://www.wizards.com/default.asp?x=dnd/mb/20050209a

The OA prestige class Shapeshifter (updated in Dragon 318) gains Wildshape based off character levels instead of levels in the prestige class.

Edit: Savage Vampires (Dragon mag 348) also get Wildshape as a Druid of 10 plus half their HD (note that they have an LA of 6).

[nijineko]

Doesn't that mean prestige only if you have no Druid levels? Afb, I'll check later

[Bastian]

Doesn't that mean prestige only if you have no Druid levels? Afb, I'll check later

There is no requirement that the character be a non-Druid. Why do you ask/What gave you that impression?

[nijineko]

Ah, sorry. Slight miscommunication on my part. You are correct, can be druid. My point was simply that those two prestige are ways of gaining wildshape  without being a druid. 

[cru]

added shapechanger and savage vampire to the how-to-get-wildshape list
bear warrior gets a different ability