The Archivist Handbook v2

[Mooncrow]

3.5 Archivist Handbook

This guide is a remake of Phaxi's original Archivist Handbook and the format is modeled on After Crecent's Cleric Handbook  This is very much a work in progress, and I am open to comments, criticisms, and suggestions.

Table of Contents

• Post 1: Introduction and Party Role
• Post 2: Attributes and Races
• Post 3: Class Features
• Post 4: Feats and Skills/Skill Tricks
• Post 5: Spells
• Post 6: More Spells (and how to get them)
• Post 7: Equipment
• Post 8: Multiclassing, Dips, and Prestige Classes
• Post 9: Sample Builds
• Post 10: Debatable Tactics/Tricks and Credits

Introduction
Lore-wise, the archivist is the seeker of buried secrets and forgotten lore.  They seek out both obscure divine spells and knowledge about the creatures of the darkness.
Archivists are the divine versions of wizards; they're intelligence based, they have a spellbook (called a prayerbook), and they learn spells as a wizard does, either from scrolls, or off other archivists prayerbooks.  Now, that may not sound very strong, compared to a cleric that automatically has access to their entire list, and can also turn undead, and has access to domains, but the archivist can learn any divine spell: cleric, druid, adept, shugenja, domain spells, you name it - if it can be cast as a divine spell or written as a divine scroll, archivists can learn it.  They also get a few more nifty abilities related to knowledge skills that can buff the entire party, or daze/stun the enemy.  They can even, with the right PrC dips, have the option of using Divine Metamagic and/or access to Domains.  Overall, they are potentially one of the most versatile casters in the game, and I think, the most fun to play. 

Pros
• You can cast any divine spell in the game!
• Light and medium armor proficiency.
• Better hit dice than a wizard
• More spells per day than a wizard
• Dark Knowledge
• Only two levels where you don’t gain some sort of special ability
• More skill points than you know what to do with
• Two good saves
• Bonus feats
• All knowledge skills are class skills

Cons
• Worst BAB available (Fixable with a DMM persistent Divine Power)
• Bad reflex saves.
• Only d6 HP / level makes them relatively fragile.
• No familiar
• No undead turning (without prestige classing)
• Potential MAD
• No heavy armor or shield proficiencies
• Dependency on a prayer book.
• The DM directly controls how powerful you are (see below)

Talking to your DM
The archivist is not a class to spring on your DM without talking to them first.  The archivist has great potential, but in the wrong campaign, it's going to be a disaster.  Find out the following before deciding to play this class:
What material will be allowed in this campaign?

An archivist, more than almost any other class, has a power level that is directly proportional to how many options are allowed in the campaign. The more divine spells there are, the wider your spell list is. Here are a list of thing that if allowed, will affect your power:
• Adepts – This NPC class gives access to some divine spells earlier than most PC classes.
• Any sort of cheap trick to get any Sorcerer/Wizard spell as a divine spell – I’m not talking about domains that grant wizard spells as divine spells, but class features that allow virtually any Sorcerer/Wizard spell as a divine spell. Some examples of this include Divine Magician variant, Hexer PrC, and Favored Souls of Bahamut/Tiamat.
• Divine Bard – This variant found in Unearthed Arcana or the online SRD allows you to add any bard spell to the spell list.
• Warlock or Pre-errata Artificers – Level 12 Warlocks or Pre-errata Artificers can create any divine spell in the game. A PC, or cohort like that in your party can be a valuable asset to your Archivist.
• Any non-core divine casting class – Shugenja for example.
• Divine Prestige Classes that add more spells to the class’s spell list. (Malconvoker, Hathran, etc)

How easy is it to purchase divine scrolls?  Even obscure ones?
Will there be NPC archivists that you can pay to learn from their prayerbook?

If the DM is clearly reluctant to let you have access to a wide selection of spells, I would advise picking a different class, or being prepared to re-roll.  An archivist that can only learn their two spells per level is just kind of terrible.  But, honestly, I've never had a problem when I've sat down to talk to a DM beforehand.  Find out how he handles wizards learning new spells, then talk about the archivist.  Walk him through the class if he doesn't know it, and explain what ever your goals are.  I've found that usually some agreement can be reached. 

Role in a Party
Here are some of the potential roles that the archivist could fill - I find it's best to choose a primary role and focus on that first; most of the really powerful tricks require heavy feat and PrC level investment.  However, the archivist is still more than capable of filling any of these roles as a secondary function with minimal investment. 

Healer: The archivist has access to every heal spell in the game, several earlier than the cleric or druid.  So, if that's what you really want to do, the archivist makes a great healer.  That said, like many members of this board, I consider healing to be a sub-par role.  Even without any feats devoted to it, you'll still be able to do the job when needed.  Have a heal or two memorized for emergencies, and call it good. 

Buffer: Here's an area that the archivist can really shine.  With access to almost every worthwhile buff in the game, and the ability to use Divine Metamagic to Persist or Quicken your buffs, you can either start the day off by throwing up a bunch of 24 hours buffs, or quickly put them up once engaged in battle.  Add in your Dark Knowledge class feature to give them +hit, +damage, and +saves with Move Actions, and the party will love you. 

Summoner:  This is my favorite role to play, and another real strength of the archivist.  With access to both Summon Nature's Ally and the Summon Monster Series (and the Summon Undead series), along with the Planar Ally/Binding lines, the archivist is an unparalleled summoner.  SNA gives you heavy combat types, while SM gives you utility and a host of supernatural abilities.  Use Rapid Spell and Divine Metamagic Twin Spell for quick deployment, and consider PrCs like the Thaumaturgist or Malconvoker for some decent boosts.

Battlefield Control: starting out with the old standby of entangle, you have all the tools for the job: divide up your enemies and conquer. 

Blaster: the archivist isn't quite as good at this as you might think; sure they have access to a lot of the good blasting spells, especially from the druid list, but most of the really good blasting PrCs are arcane-only.  Still, blasting is a crappy job anyway; it's never a bad idea to have a good damage spell or two available as a last resort, but if you have to use them, something has gone horribly wrong.

Other Roles:
Melee:  The archivist can gish it up if need be; DMM Persist of Divine Power and other tricks come in handy, but it's probably going to take several levels to come online.  Still, it's certainly doable - if anyone has any suggestions for tips/tricks/builds, please let me know.
Ranged:  The cleric archer is a standby on these boards, and with good reason: Zen Archery makes clerics very very good.  Sadly, it doesn't really work for archivists.  Archivists run off int more than wis (completely off int with the right feats) and so most archivists will be dumping wis.  So I'm going to say "just say 'no' to ranged archivist builds". (though, if there's a counter argument out there, I'm open to hearing it)

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.
To be continued...

[Mooncrow]

Attributes

    Str: Only important if you plan on being a gish, for everyone else, dump this.
    Dex: Handy to boost your Reflex save (your one low save) and for ranged touch attacks.  If you play an Illumian, you can also use Dex for your bonus spells instead of Wis. 
    Con: Con is good for every class
    Int: The money stat - all your spell DCs are based on this, plus you'll need some for your Dark Knowledge checks, and with Academic Priest, Int can also determine bonus spells.  Max this.
    Wis: If, for some reason, you can't take Academic priest, this raises in value a lot, as it determines bonus spells per day.  Otherwise, your will save is your best save, and this stat isn't worth putting many points into.
    Cha: Diplomacy is a class skill, and quite useful if you're planning on using the Planar Ally line, or straight cha is useful for Planar Binding, and probably most importantly, since Turning is trivial to pick up with this class, it fuels DMM.  If you're not planning on doing any of that, this drops to a red stat.

Races

LA +0

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Human^PHB - as always, a strong choice.  An extra feat for a feat hungry class and the extra skill doesn't hurt either.
Strongheart Halfling^FRCS - an extra feat, -2 str, +2 Dex along with small size benefits.  Another strong choice.
Kobold  - not very good on it's own merits, but with the Dragonwrought feat, +3 to all mental stats, and access to other Dragon goodies. 
Lesser Tiefling^PGtF - +2 Int, +2 Dex, -2 Cha, and some other abilities - it's not a bad choice if you aren't going for DMM
Shifter^ECS - wait, what?  -2 Int, -2 Cha, +2 Dex and it's a green?  For one reason; it gives you access to the very good Moonspeaker PrC, otherwise, stay away.
Illumian^RoD - has some interesting options, mainly the ability to sub Dex for Wis and the possibility to do some early access tricks for PrCs
Whisper Gnome^RoS - nothing particularly great for archivist, but they're just so all around good; +2 Dex, +2 Con, -2 Str, -2 Cha, small size, 30 ft move, and some SLAs
Spellscale^RotD - the stats are pretty meh, but it gives you the [dragonblooded] subtype, and a host of changeable skill bonuses and limited use metamagics. 
Grey Elves^MM - -2 Str, +2 Dex, -2 Con, +2 Int - if you want to be an elf, be this one (but seriously, don't be an elf )
all other +int elves - not really worth it

[Mooncrow]

Class Features

Hit Dice: a non-amazing d6.  You beat out wizards... and that's about it.  Staying in the back is a perfectly fine strategy^^
Skills: 4+Int per level, and given that you should have a pretty darn good int, you make a decent secondary skill monkey.  On the downside, a lot of those skill points are going to be spoken for. 
Proficiencies: Light and Medium Armor, simple weapons, no shields - break out the light crossbow and stay in the back.
Spells: Oooh, yeah.  Let's get our spell-freak on.  Cleric spells, druid spells, adept spells, domain spells, shugenja spells, paladin spells, ranger spells, blighter spells, Nentyar Hunter spells - if it can be cast as a divine spell or scribed as a divine scroll, the archivist can learn it.
Dark Knowledge:  The other part that make archivists cool - starting at 3 times per day as a move action, the archivist can make an appropriate knowledge check against the opponents (arcana for magical beast, dungeoneering for aberrations, religion for undead, the planes for elementals and outsiders) vs DC15 and either grant the entire party a boost or smite the enemy.  The frequency increases by 1/day every 3 archivist levels (4/day at 3rd, 5/day at 6th, etc)

• 1st Dark Knowledge - Tactics: DC15 - give all party members an untyped +1 bonus on rolls to hit, DC25 increase to +2,  DC35 increase to +3
• 5th Dark Knowledge - Puissance: DC15 - give all party members an untyped +1 bonus on saving throws, DC25 increase to +2,  DC35 increase to +3
• 8th Dark Knowledge - Foe: DC15 give all party members a +1d6 on damage rolls, DC25 increase to 2d6, DC35 increase to 3d6
• 11th Dark Knowledge - Dread Secret: DC15 single target is dazzled for one round, DC25 single target is dazed for one round, DC35 single target is stunned for one round
• 14th Dark Knowledge - Foreknowledge: DC15 all party members gain a +1 insight bonus to AC, DC25 increase to +2, DC35 increase to +3

Scribe Scroll: archivists gain Scribe Scroll as a bonus feat at level 1.  This is more crucial than it might seem, as it allows you to scribe scrolls for other classes spells.  From the DMG pg 282 "Note that all items have prerequisites in their descriptions. These prerequisites must be met for the item to be created. Most of the time, they take the form of spells that must be known by the item's creator (although access through another magic item or spellcaster is allowed)"
Lore Mastery: At 2nd level, the archivist gets a +2 on Decipher Script checks and +2 on the Knowledge of his choice.  Add +2 to a different Knowledge at levels 7, 13, and 17.
Still Mind: At 4th level, the archivist gets a +2 bonus to his saving throws against the school of enchantment.  One more reason not to cry about dumping Wis.

[Mooncrow]

Feats

General Purpose:

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• Academic Priest^{Legend of the Twins} - Swaps Wis to Int for bonus spells.  SAD makes for happy archivists - always take this, unless your DM doesn't allow it.
• Mother Cyst^LM - For one feat, you get a lot of nice (well, not nice so much...) options.  Very flavorful for those walking a darker path.
• Dragonwrought^RotD  - Did you choose Kobold as your race?  Yes?  Then this is the reason you did.  +3 to all mental stats for no other cost - check.  Race now effectively "dragon" - check.  Borderline cheesey feat - check.
• Leadership^PHB  - If your DM allows this feat, take it, no matter the build.  If your DM allows artificers to make divine scrolls, get an artificer for a cohort.  If not, get a warlock.  Congratulations, you now have access to every spell you want.
• Planar touchstone^PlH - a nice set of available benefits, that can be changed
• Practiced Spellcaster^CAr - if you lose a caster level through a PrC or a dip in another class, you must take this, period.
• Draconic Archivist^HoH - can use Dark Knowledge against Dragons and Constructs with a knowledge(arcana) check.
• Improved Initiative^PHB - Battles often hinge solely on who goes first - be the one that goes first.

Summoning:

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• School Focus (Conjuration)^PHB  - On its own, this feat is very terrible, however it serves as a pre-req for several much better feats, along with one of the better summoner PrCs
• Augment Summoning^PHB - +4 str +4 con to all of your summons, very nice.  You can get this from a couple different PrCs as well.
• Spontaneous Summoning^CD - probably worth it even in a non-summoner focused build, there's a lot of sheer utility offered, and it opens up some other options to you as well.
• Greenbound Summoning^LEoF - adds the quite broken Greenbound template to all of your SNA animal summons. 
• Rashemi Elemental Summoning^UE - allows you to turn your air elementals into Orglashes, and your earth elementals into thomils.
• Summon Elemental^CM - Summon a lower level elemental all day - great for scouting, trap bait, etc.
• Cloudy Conjuration - you can use your summonings as debuffs and short duration LoS/LoE blockers as well.
• Metamagic School Focus^CM - 3/day, lower the cost of metamagic on a spell of the chosen school by 1 (limit of +0) - choose Conjuration, great for getting free Rapid summons.
• Ashbound^ECS - Free Extend on all your SNA spells, and a +3 luck bonus on their to hit as well.  Only available if you take Spontaneous Summoning.
• Beckon the Frozen^Frost - You can summon you creatures as the [cold] subtype and they gain +1d6 cold damage on attacks.
• Imbued Summoning^PHBII - Cast a quickened low-level buff on your summons; pretty meh.

Metamagic:

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• DIVINE METAMAGIC - is it allowed in the campaign?  Then yes, you will take this (you will need a dip in Sacred Exorcist, or another source of turning to qualify, but that's not a big deal) and possibly more than once.  Depending on your primary role, you'll probably choose different feats to apply this to:  Persist is always a strong buffing option, and Quicken is a good option in any build.  For summon heavy builds I like Twin Spell.
• Persistent Spell^CAr - makes any personal or fixed distance spell last 24 hours at a +6 level adjustment.  Even without DMM, this is a pretty great option. 
• Twin Spell^CAr - You cast the same spell twice for a +4 level adjustment.  Great for summonings and Save or X spells. 
• Rapid Spell^CD - Full round cast spells are now a standard action for a +1 level adjustment (longer spells are affected too) - this is fantastic for summoning; summon on a standard action, then Dark Knowledge on your Move Action and your summons get the benefit too.  Not as useful for non-summoning builds.
• Quicken Spell^PHB - one of the best general utility metamagics; casting as a swift action is pretty powerful.
• Heighten Spell^PHB - very handy for making low level spells with unusual effects relevant at higher levels.
• Reach Spell^CD - give any touch spell a 30 ft range for a +2 level adjustment.  Touch attacks become ranged touched attacks, and touch spells now have a fixed distance (and can be made persistent.
• Extend Spell^PHB - kind of handy on it's own, but even more importantly, you need this to get Persistent Spell.
• Ocular Spell^LoM - Cast two spells as a full round action, for a level adjustment of +2 on each.  There are some fun uses for this, but it has a fairly narrow application.
• Sudden Maximize^CAr - 1/day apply Maximize Spell on the fly with no level adjustment.
• Chain Spell^CAr  - if this could be used to buff without jumping through a ton of hoops, it would be a great feat.
• Sculpt Spell^CAr - meh, in theory there are some decent uses for this, and if you're a primary blaster, go ahead and pick it up.
• Empower Spell^PHB - again, good for offensive spells, less good for anything else.
• Enlarge/Maximize/Silent/Still/Widen^PHB - there are too many good feats to get to worry about these; the level adjustment is simply too high for what you get from them.

Healing:

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• Seriously, don't take feats to improve this.

Devotion Feats:

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If you're doing a build that takes advantage of domains, a few of these feats can be pretty nice.
Knowledge - gain up to a +5 insight bonus on all attack and damage rolls with an appropriate knowledge check - hey, that sounds like something we already do^^  Better for a gish build or a blaster type, but anyone that ends up dealing damage on a personal basis regularly should try to get this.
Travel - 1/day move up to your speed as a swift action.  You can spend 2 turn attempts to use it again.
Law  - up to a +7 sacred/profane bonus to attack or AC that you can reallocate on a round to round basis, very nice. 
Protection  - up to a +7 sacred/profane bonus on AC for you and every ally within 30'
Animal - 1/day give yourself one of the following for one minute - up to a +8 sacred/profane str bonus, up to a +30' sacred/profane bonus to speed, flight at up to 60' speed, or a terrible bite attack.  More versatile than most of the domain feats, and sacred/profane bonuses are fairly hard to find.  Costs 3 turn attempts for extra uses though
Strength - overcome hardness, add a decent slam attack, only costs 1 turn attempt to add a daily use; overall useful
Water - not horrible, summon up to a Huge water elemental as a standard action, only costs 1 turn attempt for extra uses.  It would be nice if the other elemental devotions had this option.  Too bad water elementals are pretty meh.
Sun - massive extra weapon damage to undead
Air - it's not terrible, but you have better places to spend feats
Everything else - just say no
 

Skills

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• Concentration Every caster needs to have this maxed.
• Craft There are better uses for your skill points
• Decipher Script If your DM hints that this is going to be an important skill in the campaign, the archivist is a great choice to grab it, otherwise, no.  It's too bad really, it does fit in really well flavor-wise.
• Diplomacy Again, if the party needs a face, and you didn't dump Cha, you can do a fine job.  Also handy if you are planning on using the Planar Ally line at all.
• Gather Information  Potentially useful to track down obscure scrolls
• Heal  Potentially useful when used with the healing lorecall spell, but in general, don't bother.
• Knowledge (all)  You'll want to max at least four of these - arcana, dungeoneering, religion and the planes (you may possibly want rank in nature as well depending on what PrCs you pursue)
• Profession  Even worse than Craft skills.
• Search  Hopefully your real skillmonkey has this.
• Spellcraft  Like all casters, you will be maxing this.

Cross Class Skill of Note

• Bluff  Worth putting some ranks in if you are aiming at the Malconvoker class.

[/list]

[Mooncrow]

Spells

Spells are the archivist's greatest strength, and unless you're playing in a campaign with nigh-unlimited money, you'll want to choose your spells carefully.  Here are some of the more potent and versatile spells that you may want to pick up as fast as you can.
(For now, I'm leaving out the Divine Bard versions of spells; I'll probably go back and add them later if there's interest)

0 Level

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You get every cleric level 0, and that covers all of the important ones.

1st Level

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Cleric:
Bless^PHB - +1 morale bonus to all allies attack rolls and saves against fear effects
Command^PHB - Sleep is generally better at low levels, but this doesn't have a HD cap, so remains useful longer. 
Divine Favor^PHB - +1 luck bonus on attack and damage rolls that scales up to +6
Entropic Shield^PHB - 20% miss chance for all ranged attacks against you
Obscuring Mist^PHB - One of the best early retreat spells, drop this and run away.  Even better later on when you have pets that have blindsight or similar.
Protection from Evil/Good/Chaos/Law[sup]PHB[/sup] - a very powerful defensive spell
Sanctuary^PHB - there are a lot of non-damaging things you can do and still be effective; this lets you do them safely.
Shield of Faith^PHB - +2 deflection bonus to AC that scales up to +5
Conviction^SpC - +2 morale bonus to saving throws for one ally that scales to +5, Combine with Dark Knowledge: Puissance against nasty Save or X using foes.
Summon Monster I - not very useful at first, but at higher levels becomes a very versatile use for a 1st level slot
Omen of Peril^SpC - the first good divination spell
Lesser Vigor^SpC - The premiere out of combat healing spell

Domain: (Domain^{Domain source})^{spell source}
Mage Armor (Force^SpC)^PHB
Identify (Oracle^SpC)^PHB
Sleep (Dream^SpC)^PHB - the first save or lose spell - also available from the Adept list
Entangle (Plant^PHB)^PHB - Fantastic battlefield control.  Also available from the Druid list
Grease (Slime^SpC)^PHB
Enlarge Person (Transformation^RoE)^PHB
Detect Thoughts (Truth^RoE)^PHB - multiple uses for this, interrogation, intelligence gathering, etc

Non-Cleric: (Class^{Spell Scource})
Lesser Restoration (Pal^PHB) - heal ability score damage and cure status effect one spell level early
Warning Shout (Pal^SpC) - as an immediate action, all your allies are not flat-footed
Resist Energy (Ranger^PHB) - a good defensive spell, earlier than anyone else.
Lay of the Land (Ranger^SpC) - another good divination spell, learn about the land for 50 miles around you.
Embrace the Wild (Ranger^SpC) - gain low-light vision, scent, or blindsense for 10 minutes/level
Summon Nature's Ally I (Druid^PHB) - really short duration at first, but the wolf is really good - free trip attacks
Shillelagh (Druid^PHB) - makes a quarterstaff a really good melee weapon
Winged Watcher (Druid^CSc) - turn into a bird as a swift action.  Flight at level 1?  Yes, please.  Only lasts 1 round/level, but still, it's nice to have that option.  Great escape spell.
Camouflage (Druid^SpC) - +10 on Hide checks
Aspect of the Wolf (Druid^SpC) - effectively turn into a wolf for 10 minutes/level
Produce Flame (Druid^PHB) - one of the more potent blasting options at this level.
Barkskin (Nentyar Hunter^PHB) - scaling natural armor bonus, also available from the Druid list or Plant Domain

2nd Level

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Cleric:
Bull's Strength/Eagle's Splendor/Owl's Wisdom/Bear's Endurance^PHB - these tend to come in handy quite a bit.
Desecrate^PHB - vital if you're going to be animating the dead
Hold Person^PHB - save or lose
Spiritual Weapon^PHB - a tool for dealing with incorporeal foes
Summon Monster II^PHB - not as good as the other two summon spells available, but decent if you don't have access to them.
Brambles^SpC - a melee buff for wooden weapons.
Close Wounds^SpC - one of the better healing spells - an immediate action spell for those desperate moments.
Divine Insight^SpC - gives a scaling bonus between +8-15 for any one skill check.
Ghost Touch Armor^SpC - adds the Ghost Touch ability to your armor.
Living Undeath^SpC - makes the target immune to criticals and sneak attacks
Summon Undead II^SpC - the owlbear skeleton is slightly better at combat than the SNA hippogriff
Lore of the Gods^CC - Grants a +5 (+10 if you worship a god with the Knowledge domain) insight bonus on all knowledge checks for 10 minutes/level
Substitute Domain^CC - really great for later on, if you decide to play around with domains.
Darkbolt^LoM - 1d8/2 caster levels damage and must save or be stunned for one round

Domain:
Magic Missile (Force^SpC)^PHB - nothing exciting, but it's a handy spell every once in a while
Fox's Cunning (Baator^SpC)^PHB - the buff spell that you really care about, also from the Divine Bard list
Locate Object (Travel^PHB)^PHB - a solid divination spell, and at a lower level than usual
Cat's Grace (Celerity^SpC)^PHB - and just to round the buff list out, also off the Adept list
Ghoul Glyph (Hunger^SpC)^SpC - gives you something to do in your downtime (when you're not learning new spells )
Magic Circle Against Evil (Exorcism^ECS)^PHB - in addition to being generally good defense, these are also vital to several higher level spells.
Invisibility (Lust^SpC)^PHB - also off the Adept list
Alter Self (Transformation^RoE)^RoE - one of the most versatile spells available, boost your AC, grab bonuses to skills, fly, etc. 
Summon Dire Hawk (Sky^RotW)^RotW - not as powerful as the other summons at this level, but this spell is minutes/level instead of rounds/level, making it an interesting option.  Also off the Druid list.
Demoncall^FCI Demonic^FCI - a +10 profane bonus to knowledge arcana, religion or the planes for any one check.  Great for use with Dark Knowledge.

Non-Cleric:
Summon Nature's Ally II (Druid^PHB)- Hippogriff is the strong one here, a good combatant and some flying powah.
Mass Snake's Swiftness (Druid^SpC) - all of your allies make one melee or ranged attack.  If you did nothing with your second level slots aside from memorize this spell, you would probably be fine.
Blinding Spittle (Druid^SpC) - Blind a target with no save, lasts until they rinse their eyes out.
Mass Camouflage (Druid^SpC) - +10 Hide for the whole group
Bite of the Wererat (Druid^SpC) - another close combat buff
Creeping Cold (Druid^SpC) - 6d6 over 3 rounds, extend it at higher levels for 21d6 for a 3rd level spell
Heart of Air Druid^CM - +10 on jump checks, +10 fly speed, swift action feather fall
Splinterbolt (Druid^SpC) - not quite as good as Scorching Ray, unless you're fighting immune to fire types.  It's ranged attack instead ranged touch, and is affected by DR.  It does have a crit range of 18-20 though.
Scorching Ray (Adept^PHB) - probably the best blasting spell of the level, 4d6 on a ranged touch attack, no save
See Invisibility (Adept^PHB)
Mirror Image (Adept^PHB) - one of the best defensive spells in the game
Web (Adept^PHB)
Tremorsense (Ranger^SpC) - gain tremorsense 30'
Primal Instinct (Ranger^DM) - 24 hour buff, gain +5 competence bonus to Initiative and Survival.  When stacked with another Primal spell, gain Uncanny Dodge.

3rd Level

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Cleric:
Animate Dead^PHB - start that undead horde up!  (Or, if you're smarter, a small group of elite undead)
Dispel Magic^PHB - magic is where the power is; make sure that you can fight back when the other side has it.
Magic Circle Against Evil/Good/Chaos/Law^PHB - in addition to being generally good defense, these are also vital to several higher level spells.
Magic Vestment^PHB - never spend money upgrading your armor enhancement bonus.
Protection from Energy^PHB - damage absorption for an energy type chosen at cast time.
Summon Monster III^PHB - this one is where SM starts to get good.  Most of your animals should have DR 5/magic, and you get your first demon, who can cast stinking cloud for you. 
Mass Conviction^SpC - boost your whole party's saving throws
Mass Resist Energy^SpC
Mass Lesser Vigor^SpC - a favorite of DMM Persist, the ultimate in out of combat healing.
Sonorous Hum^SpC - no need to stop casting when you have a concentration spell up.
Spikes^SpC - the next upgrade of the wooden melee weapon line
Summon Undead III^SpC - the troll skeleton is a decent beatstick, if he can get a full attack in, he's better than the dire wolf from SNA III

Domain:
Anyspell (Spell^SpC)^SpC - for those going into Domain shenanigans.
Blur (Celerity^SpC)^PHB - another 20% miss chance spell, this one works against melee as well
Fly (Travel^PHB)^PHB - real flight
Haste (Time^SpC)^PHB - haste is really, really good; and it affects 1 creature/level, so even when you fist get it, you can likely haste your entire party
Gaseous Form (Air^PHB)^PHB - good escape spell
Suggestion (Dominate^SpC)^PHB
Displacement (Illusion^PGtF)^PHB
Distilled Joy (Joy^BoED)^BoED - creating scrolls takes money and XP, this can help offset some of the latter.
Plant Growth (Plant^PHB)^PHB - not very good on it's own, but needed to get into the Holt Warden PrC
Vampiric Touch (Necromancy^ECS)^PHB
Divination (Oracle^SpC)^PHB - more useful Divination^^
Dimensional Anchor (Portal^PGtF)^PHB - stop teleporters cold.  (also really important when binding)
Tongues (Commerce^ECS)^PHB
Recitation (Purification^SpC)SpC
Evard’s Black Tentacles (Blackwater^Storm)^PHB - only useful for a couple levels, after that, your better off with summons doing your grappling.

Non-Cleric:
Spike Growth (Druid^PHB) - put a real crimp in a charger's day.
Summon Nature's Ally III (Druid^PHB) - the dire wolf is a toss up with the undead troll, the wolf hits harder on a single attack and has a higher move, and like the smaller version, can trip for free.
Wind Wall (Druid^PHB) - Completely shut down archers, swarms, and tiny fliers.
Bite of the Werewolf (Druid^SpC) - another melee buff, hopefully by this point you aren't having to use these much any more, but they're a nice stat boost when you think you might have to get close to the enemy.
Crumble (Druid^SpC) - destroy objects, this spell ignores hardness
Icelance (Druid^SpC) - 6d6 damage and they have to save or be stunned for 1d4 rounds.  Not great, but when you need to blast, it's not bad.
Spiderskin (Druid^SpC) - Barkskin + saves against poison and racial bonus to Hide.
Arctic Haze (Druid^Frost) - Obscures vision and does damage. 
Venomfire (Druid^SK) - seriously, just say no to this spell if you want to avoid books being flung at your head.  The most broken damage spell in the game.
Primal Senses (Ranger^DM) - 24 hour buff, gain low-light vision and +5 competence bonus to Spot and Listen.  When combined with another Primal spell, gain Uncanny Dodge.
Lightning Bolt (Adept^PHB)
Charm Monster (Emissary of Barachiel^PHB) - more enchantment cheatery - so fun^^
Lesser Geas (Emissary of Barachiel^PHB) - for those pesky Planer Bindings that just won't give in.
Scrying (Emissary of Barachiel^PHB) - the gold standard of long distance problem solving.
Freedom of Movement (Nenytar Hunter^PHB) - critical to stop grapples and other nasty effects.
Death Ward (Consecrated Harrier^PHB)
Restoration (Healer^PHB) - cure permanent ability drain
Greater Magic Weapon (Pal^PHB) - never pay for weapon enhancements again

4th Level

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Cleric:
Air Walk^PHB - a very good way of getting over larger obstacles.
Dismissal^PHB - get rid of a single outsider.
Divine Power^PHB - What was your BAB?  Doesn't matter, now you have the BAB of a fighter, and extra hit points, and +6 to strength. 
Imbue with Spell Ability^PHB - a lot of useful tricks with this one.
Giant Vermin^PHB - makes some pretty decent beatsticks
Lesser Planar Ally^PHB - a fairly bad spell by itself, but you need it to qualify for Thaumaturgist
Spell Immunity^PHB - really good if you're going against known enemies, or to stop some of the more common nasties.
Summon Monster IV^PHB - some decent SLAs and the Howler makes a good debuffer against tougher opponents.
Mass Shield of Faith^SpC - scaling deflection AC bonus for the whole party
Panacea^SpC - cure almost any status
Sheltered Vitality^SpC - several good immunities
Summon Undead IV^SpC - pretty lackluster.  The zombie has a lot of hps, but that's about it, the ghast and allip might as well just be an aoe spell (and not a very good one)
Greater Resistance^SpC - 24 hour duration, +3 to all saves
Planar Tolerance^SpC - ignore negative effects of other planes.

Domain:
Leomund's Secure Shelter (Cavern^SpC)^PHB - this isn't a good spell at all, but it's one that I really like anyway^^
Chaos Hammer/Order's Wrath/Holy Smite/Unholy Blight (Chaos/Law/Good/Evil^PHB) - damage + effect to appropriate outsiders
Good Hope (Charm^SpC)^PHB - 1 target/level gets a +2 morale bonus to every action for 1 minute/level
Glibness (Commerce^ECS)^PHB - +30 to non-combat Bluff checks
Enervation (Decay^ECS)^PHB - target loses 1d4 temporary levels
Dominate Person (Domination^SpC)^PHB - Take control of a humanoid for 1 day/level
Wall of Fire (Fire^PHB)^PHB - not nearly as good as some of the other walls, but it has it's uses.  It's probably best at burning down wooden structures.
Otiluke’s Resilient Sphere (Force^SpC)^PHB- multi-use spell, it's a great defense for yourself, or it's a good way to take one enemy out of the fight. 
Modify Memory (Mentalism^SpC)^PHB - oh, the number of problems this spell has solved for my group over the years...
Dimension Door (Travel^PHB)^PHB - the first really solid teleport spell.  Limited distance, but still solves a lot of problems.
Explosive Runes (Rune^SpC)^PHB - a good spell for casting on off days; get creative with its uses!
Shadow Conjuration (Shadow^ECS)^PHB - like all of the shadow spells, extremely versatile.
Slow (Sloth^SpC)^PHB - one of the standard "save or suck" spells

Non-Cleric:
Bite of the Wereboar (Druid^SC) - high +Con and + Nat. Armor
Blast of Sand (Druid^Sand) - a solid spell against creatures with SR
Boreal Wind (Druid^Frost) - solid damage + knockback effects and persists without the need for concentration.  Also has a huge range. 
Flame Strike (Druid^PHB) - good damage, and half of it bypasses immunity/resistance to fire. 
Vortex of Teeth (Druid^SpC) - really nasty if you can drop it on slowed/immobilized enemies.  Works against incorporeal creatures as well.
Greater Creeping Cold
Heart of Earth (Druid^CM) - gain CLx2 temporary hit points and a +8 bonus against trip attacks, bull rush, and overrun.  As a swift action, activate a stoneskin effect that last for rounds/level and ends the entire buff when finished.  No component.
Summon Nature's Ally IV (Druid^PHB) - this is a really great level for this spell line - brown bear and croc are great grapplers (bear for more damage, croc for better lockdown), the tiger is a pouncing damage machine, and the unicorn is a mini-healer that can also dish out some decent damage.
Primal Speed (Ranger^DM) - 24 hour buff, +5 to Ref saves, +10 to move.  When combined with another Primal spell, gain Uncanny Dodge.
Animal Growth (Ranger^PHB) - one of the best buff spells in the game.
Legend Lore - Consecrated Harrier^PHB - divination
Break Enchantment (Paladin^PHB) - good for getting rid of some of the more unusual curse types.
Wall of Thorns (Nentyar Hunter^PHB) - solid battlefield control.
Polymorph (Adept^PHB) - so abusable, but so nice.
Stoneskin (Adept^PHB) - expensive, but effective when you need it.  Heart of Earth is probably more effective though, if Complete Mage is allowed.
Telepathic Aura (Paladin^SpC) - telepathically communicate with all your allies.
Summon Giants (Disciple of Thrym^Frost) - wait, what?  Summoning CR11 monsters?  Prepare to dodge thrown books, but damn, that's sexy.

5th Level

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Cleric:
Plane Shift^PHB - yay, the first interplanar travel spell!
Righteous Might^PHB - it's like Enlarge Person, only much better
Spell Resistance^PHB - Annoyed by your spells fizzling against outsiders?  Now let them feel your pain.
Summon Monster V^PHB - some solid SLA's, probably the best choice against large groups of mooks
True Seeing^PHB - I really can't emphasize enough how useful this spell is.
Wall of Stone^PHB - good battlefield control, or use it for building your new doom fortress
Swift Etherealness^PH2 - pinned in by enemies?  swift action turn ethereal, and then move out of danger.
Divine Agility^SpC - it's not a huge improvement over Bite of the Wererat - this really should have been insight instead of enhancement.  But, if you or a party member really need that little extra, it can be useful.
Revivify^SpC - resurrect a fallen comrade within one round and they don't lose a level.  It's worth carrying around the 1000g in components.
Righteous Wrath of the Faithful^SpC - +3 morale bonus to attack and damage rolls + an additional attack on a full attack.
Summon Undead V^SpC - and the last of the Summon Undead line goes out with a whimper.  1d3 brown bears from SNA V destroys anything on this list.
Triadspell^SpC - A really great spell.  Cast it during downtime, and effectively triple your lower level spell slots.  Ok, that may be an exaggeration, but it doesn't go away unless you cast the spells, or prepare another spell in the slot.  And there's no limitation on how many slots you can cast it on.
Surge of Fortune^CC - gain a +2 luck bonus on just about everything - end the spell early to get a natural 20 on a roll.

Domain:
Control Winds (Air^PHB)^PHB - absolutely wreck things with this spell.
Fabricate (Artifice^ECS)^PHB
Passwall (Cavern^SpC)^PHB
Valiant Fury (Courage^SpC)^SpC - morale bonus to Str and Con and Will save + extra attack when using a full attack
Major Creation (Creation^SpC)^PHB
Hallucinatory Terrain (Gnome^SpC)^PHB - these are neat, but only if there isn't another illusion caster in the group, otherwise, don't bother.
Persistent Image (Illusion^SpC)^PHB
Wall of Iron (Metal^SpC)^PHB - like wall of stone, only potentially more profitable, if the DM lets you get away with that sort of thing.
Prying Eyes (Orc^SpC)^PHB - little spies scout out the surrounding area and report back to you
Mass Eagle’s Splendor (Pleasure^BoED)^PHB
Teleport (Travel^PHB)^PHB - and now we have real travel. 
Lesser Planar Binding (Rune^SpC)^PHB - And, probably my favorite line of spells in the game.
Shadow Evocation (Shadow^ECS)^PHB - the shadow conjuration/evocation line is just so handy at increasing the types of tricks we can do.
Permanency (Time^SpC)^PHB - there are some pretty handy things you can do with this.

Non-Cleric:
Commune with Nature (Druid^PHB)
Awaken (Druid^PHB) - a neat way to get some additional cohort-like creatures; be sure to clear this with your DM first, though.  It's annoying to spend the xp, and then have the DM say "and then the animal goes on it's merry way without you".
Baleful Polymorph (Druid^PHB) - turn your enemy into a harmless little bunny.  Hugging, squeezing and calling him "George" are optional.
Bite of the Weretiger (Druid^SpC) - large Str boot, and Power Attack
Summon Nature's Ally V (Druid^PHB) - The elemental has some uses, especially if you have Rashemi Elemental Summoning, but for combat, the 1d3 brown bears are probably the best bet.
Owl's Insight (Druid^SpC) - best Wis buff - insight bonus equal to 1/2 caster level
Phantom Stag (Druid^SpC) - a really fast mount with some nice extra abilities
Cloak of the Sea (Druid^SpC) - mandatory if there's any underwater action in the campaign.
Heart of Fire Druid^CM - +10 to land speed, 10 fire resist, and as a swift action can give you flame shield.  If two or more Heart spells are up, gain light fortification.  If all four are up, gain heavy fortification.
Heal (Adept^PHB) - the most (only?) useful in-combat healing spell.
Antilife Shell (Blighter^PHB) - keep out all living things
Forbiddance (Blighter^PHB) - Permanently seal off a space from planar travel.
Find the Path (Nentyar Hunter^PHB) - never, ever get lost again.

6th Level

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Cleric:
Greater Dispel Magic^PHB - a much higher limit on the caster check; a must have.
Heroes' Feast^PHB - it's basically a 12 hour version of Aid with immunity to fear added.  It's move of a convenience spell than anything else.  Get it, but at a fairly low priority.
Planar Ally^PHB - in theory, this can come in handy.  Honestly, I usually pick it up just so I have all the summoning/calling spells; I don't think I've ever used it.  The cost, even with thaumaturgist, is just too bloody high.
Summon Monster IV^PHB - from here on out, the difference between SM and SNA is basically the same at every level - SM has the better survivability and the better SLAs, SNA has the better beatsticks; especially if you have elemental boosting feats.  It's really handy to have both.
Word of Recall^PHB - not super important if you have teleport, really nice if you don't.
Energy Immunity^SpC - complete immunity from one energy type for 24 hours.
Superior Resistance^SpC - +6 to all saving throws for 24 hours
Stone Body^SpC - gain construct-like immunities and DR
Spiritual Guardian^CC - either gain a +6 deflection bonus to armor, or have another creature attacking on your side.  A good spell to cast right before going into battle, when you're not sure what's waiting for you.

Domain:
Greater Anyspell^SpC - Spell^SpC - if you have real domain spell slots, with this you can cast any sorc/wiz spell up to 5th level.
Contingency^PHB Time^SpC - there are a lot of possibilities with this.
Magic Jar^PHB Envy^SpC - Possession
Chain Lightning^PHB Air^PHB - it's blasting, but less bad than most at this level.
Greater Heroism^PHB Passion^ECS - +4 morale bonus to attacks, saves, and checks, 1/level temporary hps, and immunity to fear.
Antimagic Field^PHB Magic^PHB - sometimes the bad guys have the better magic; shut them down when they do. 
Probe Thoughts^SpC Mind^SpC - great interrogation spell.
Eyebite Necromancy^ECS - long lasting debuff on 1 enemy per round as a move action.
Shadow Walk^PHB Shadow^ECS - take a walk in the Plane of Shadow
Force Shapechange^RoE Truth^RoE - force shapechangers to stay in their true form; great for stopping a druid.
Cloudwalkers^SpC Windstorm^SpC - 1 person/level gains flying 60' (perfect)
Planar Binding^PHB - again, my favorite line of spells in the game; incredibly powerful.

Non-Cleric:
Bite of the Werebear^SpC Druid - the last of the Bite line, this one is a massive Str and Con and Natural Armor boost.
Enveloping Cocoon^SpC Druid - effectively turns a Fort or Will save into a Reflex save.  Situational usefulness, would be better if it affected creatures over large size.
Greater Scrying^PHB Druid - longer lasting than Scrying.
Spellstaff^PHB Druid - unless you're fighting every day, this is effectively an extra spell slot of your highest level.  A must have.
Tortoise Shell^SpC Druid - a +6 -9 enhancement to natural armor.  Acts as heavy armor though =/
Summon Nature's Ally VI^PHB Druid - Huge Elementals, Large Storm Elementals, Dire Bear for tearing non-grapplers to little bits, Oread^FF that can cast earthquake(!) - there's lots to like at this level.
Mephit Mob^Sand Druid - summon 2d6 mephits for 10 minutes/level; you choose type. 
Transport via Plants^PHB Druid - like word of recall, mostly useful if you haven't learned teleport yet.
Greater Restoration^PHB Healer - only use to fix permanent level loss; everything else can be taken care of without the xp loss.
Regeneration^PHB  Healer - again, a rather specialized spell, but really good to have when you need it.
Antipathy^PHB Blighter -
Finger of Death^PHB Blighter - save or die; save vs fort.

7th Level

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Cleric:
Blasphemy/Holy Word/Dictum/Word of Chaos^PHB - a no save area effect spell, with various penalties depending on HD difference.  A great mook killer.  Also banishes outsiders (Will save allowed vs banishing)
Ethereal Jaunt^PHB - hop over to the Ethereal Plane either to deal with an ethereal creature or to avoid something on the Material Plane.
Resurrection^PHB - even if there's a cleric in the party, it's nice to have this.  Combine it with Cocoon when you get it to have true resurrection one spell level early.
Refuge^PHB - nice for letting the non-casters in the party have a way of teleporting home.
Destruction^PHB - save or die, and even on a save, the target still takes 10d6.
Summon Monster VII^PHB - some nice SLAs here - Wall of Ice at will, Dispel Magic at will, Major Creation (vegetable matter is permanent - lots of ways to abuse that)
Greater Consumptive Field^SpC - a nasty spell, but with some pretty huge benefits.  Gain up to half again your CL by killing everything around you with 9 hps or less.  For true Evil Overlord tactics; persist this and walk through towns.
Holy Star^SpC - a good multi-use spell - gain either spell turning, +6 circumstance bonus to AC, or do 1d6 damage for every 2 levels.  The spell lasts 3 rounds and you can choose which effect each round.
Holy Transformation^SpC - take on the aspect of a hound archon; you become an outsider and gain several abilities.
Greater Plane Shift^SpC - like plane shift, without the random arrival point.
Fortunate Fate^SpC - a contingent heal, that goes off if the target is about to die. 

Domain:
Animal Shapes^PHB Animal^PHB - polymorph for the whole party; animal only, and it lasts for hours/level
Hardening^ECS Artifice^ECS - increase the hardness of an item permanently by 1 point per 2 levels.  Otherwise known as the "sunder this, bitch" spell.
Disintegrate^PHB Destruction^PHB
Earthquake*^PHB Earth^PHB - a great spell, but I almost never memorize it since it can be cast by a summon from SNA VI.  So, not worth getting.
Mordenkainen’s Magnificent Mansion^PHB Feast^ECS - a much more elaborate rope trick, it doesn't see much use, but every once in a while it can come in really handy.  I usually carry a scroll of this.
Forcecage^PHB Force^SpC
Screen^PHB Gnome^SpC - good protection against scrying.
Project Image^PHB Illusion^SpC create a quasi-real duplicate of yourself
Starmantle^BoED Joy^BoED - non-magical weapons are destroyed when they try to touch you.  All attacks with magic weapons are halved in damage if you can make a reflex save vs DC15
Spell Turning^PHB Luck^PHB - bounce back 1d4+6 levels of spells back at the caster.
Brain Spider^SpC Mind^SpC - mentally eavesdrop on up to 8 creatures.
Etherealness^PHB Portal^SpC - turn ethereal, can take others with you.
Drawmij’s Instant Summons^PHB Rune^PGtF - summon a marked item to you from anywhere in the multiverse.
Greater Shadow Conjuration^PHB Shadow^ECS
Reverse Gravity^PHB Sky^RotW
Limited Wish^PHB Envy^SpC
Bigby's Grasping Hand^PHB Strength^PHB
Moment of PresciencePHB Time^PGtF - gain an insight bonus equal to CL on any one roll. I love this for making difficult binding checks.
Greater Teleport^PHB Travel^PHB - like teleport but no range limit and no chance of missing the target.
Illusion Purge^RoE Truth^RoE
Acid Fog^PHB Water^PHB - like solid fog, but everything takes 2d6 per round.
Tenser's Transformation^PHB Hero^OA

Non-Cleric:
Summon Nature's Ally VII^PHB - 1d3 Huge elementals or a huge storm elemental. 
Master Earth^SpC Druid - druid teleport, without the teleport; which means it's not blocked by the usual anti-teleport measures.  Incredibly useful.
Storm Tower^SpC Druid - a solid defensive buff, if excessively flashy.
Teleport Object^PHB Shugenja - why carry treasure when you can just send it back to your base?

8th Level

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Cleric:
Dimensional Lock^PHB - have this readied when using binding spells on creatures with teleport.
Discern Location^PHB - locate any creature or object, the only things that stop it are mind blank and the direct intervention of a deity.
Greater Spell Immunity^PHB - now be immune to certain spells of up to 8th level.
Cloak of Chaos/Holy Aura/Shield of Law/Unholy Aura^PHB - party wide SR 25, along with protection from evil-type effects.  Anyone that lands a melee attack on someone guarded by this spell has to save or be afflicted by a status effect.
Greater Planar Ally^PHB - still expensive for what you can get with it.
Summon Monster VIII^PHB - a whole host of new SLAs to choose from
Summon Giant^Frost - repeating this on the list since, while you can technically get it at 4th level, no sane DM would allow that, and this is one of the few summon spells that will do a decent job if you haven't been concentrating on summoning.
Mass Death Ward^SpC
Heat Drain^SpC - deal 1d6/level to everyone in a 20' radius, gain 2 temporary hps for every creature effected.
Stormrage^SpC - gain flying and immunity to ranged attacks; every round you can deal 1d6/level lightning damage to a single target with no saving throw. 

Domains:
True Creation^PHB Artifice^ECS
Greater Blink^SpC Celerity^SpC - like blink but with much more control over the effects.
Analyze Dweomer^PHB Commerce^ECS
Iron Body^PHB Earth^PHB - gain several construct immunities and DR
Mind Blank^PHB Protection^PHB - almost complete protection against scrying and mind affecting spells.  This is a must have, or an item with this effect up permanently.  (ideally both)
Incendiary Cloud^PHB Fire^PHB - use this as battlefield control.
Otiluke’s Telekinetic Sphere^PHB Force^SpC
Otto’s Irresistible Dance^PHB Gnome^SpC - no save debuff, basically a "you lose" button.
Polymorph Any Object^PHB Trickery^PHB - powerful enough to be banned in a lot of campaigns. 
Greater Shadow Evocation^PHB Shadow^ECS
Bigby’s Clenched Fist^PHB Strength^PHB - the hand of force automatically attacks and stuns each round.
Foresight^PHB Time^SpC- never be caught flat-footed, gain warnings of what to do to avoid immediate danger.
Phase Door^PHB Travel^PHB - create invisible passages through walls, etc.
Greater Planar Binding^PHB Demonic^BoVD - bind up to 18HD.
Giant SizeOA Hero^OA

Non-Cleric:
Summon Nature's Ally VIII^PHB Druid - the elementals continue to be the powerhouse choices. 1d3 greater, or 1 greater storm are the best options.
Whirlwind^PHB Druid - remove enemies from the fight while dealing damage.
Frostfell^Frost Druid - area effect save or turn to ice, on a successful save, still take 1d6/level.
Leonal's Roar^BoED Druid - holy word + damage.
Cocoon^SpC Druid - combine with resurrection to get true resurrection, ie no level/Con loss.
Mass Heal^PHB Healer

9th Level

(click to show/hide)

Cleric:
Astral Projection^PHB
Energy Drain^PHB
Gate^PHB the big brother of the planar ally series, this one at least can call creatures big enough to make the xp hit worthwhile. 
Miracle^PHB - the most versatile spell in the game, like wish but the spell replication costs no xp and there are fewer limitations. 
Summon Monster IX^PHB - and this may run fairly close behind it; almost 100 SLAs available, and they bring their own beatstick with them. 
Summon Elemental Monolith^SpC - remember back in the level 3 spells when I told you to get sonorous hum?  Yeah, this spell is why.  Summons a CR17 elemental, requires concentration for as long as it's up. 
Greater Visage of the Deity^SpC - really good if you can persist it, this spell offers several untyped and racial bonuses.

Domain:
Prismatic Sphere^PHB Sun^PHB - a powerful defensive spell
Time Stop^PHB Trickery^PHB - another "so powerful it's often banned" spell. 
Bigby’s Crushing Hand^PHB Strength^PHB
Mordenkainen’s Disjunction^PHB Magic^PHB
Teleportation Circle^PHB Rune^SpC
Shades^PHB Shadow^ECS - just like shadow conjuration, but up to 8th level spells and 80% real.
Summon Devoted Roc^RotW Sky^RotW - this summon isn't particularly powerful unbuffed, but it lasts for hours/level.
Mass True Seeing^RoE Truth^RoE

Non-Cleric:
Shapechange^PHB Druid - like polymorph on crack, shapechange gives you the extraordinary and supernatural abilities of the form along with the physical stats.  And, you get to still cast spells in quite a few of them.
Summon Nature's Ally IX^PHB Druid - fairly disappointing; though still not bad for summoning a horde of greater storm elementals
Tsunami^SpC Druid - 1d6/level every round and huge modifiers for those caught in the wave to do anything.  Anything Huge or smaller is pretty much dead unless they can teleport out.  The component is super-expensive though; best when used as an SLA. 
Shambler^PHB Druid - handy to have as guards for the home base, or when you need a few extra disposable bodies.

[Mooncrow]

Ways of getting non-cleric divine spells:

If you're in a "Magic-Mart" kind of world, then it may be as easy as tossing down your money for any scroll you want.

Find a member of the class in question and pay them to help you scribe a scroll (barely cheaper than just buying a scroll)

Find an archivist NPC to trade spells with or pay to borrow his prayerbook (50g x spell level) + (100 x spell level to scribe into the spell book)

12th level+ Warlock can scribe divine scrolls of any divine spell after making a DC 25 + spell level UMD check. 

A Chameleon can prepare spells and therefore make scrolls from any divine list up to 6th level.

Research: First of all, let's just accept that spell research in 3.5 is poorly written and ill-defined and move past that.  What we want to do as an archivist is research existing spells, and since we're pointed to the wizard section on learning new spells, and wizards can research existing spells, we should be able to as well.  With me so far?  Good.  So, the only rules for researching existing spells are given on page 198 of the DMG - it takes one day and costs (10 x spell level x caster level x2), so about a 20% savings over buying a scroll, before we count scribing the spell into the prayerbook.

No matter what method you use, expect to spend at least half of your WBL on getting new spells.  Flexibility comes at a price.

Sources for non-divine spells as divine:

Domain Spells - all domain spells are fair game; and with the huge number of domains throughout the books, that's a large percentage of the sorc/wiz list right there.

Divine Bard (UA Variant) - if these exist, that's the entire bard list as divine.

Divine Magician (CM acf) - can get all divination, necromancy, and abjuration sorc/wiz spells as divine.

Various Initiate-type feats add spells to divine lists.

Hexer (MotW PrC) - a 3.0 class, but not updated so should still be fair game.  Can learn any sorc/wiz spell as divine.

Favored Soul of Bahamut/Tiamat (DrM acf) - can learn any sorc/wiz spell up to 6th level as divine.

Southern Magician (RoF feat) - allows any arcane spell to be cast as divine (and vice versa).  It is slightly questionable how useful this one is, since it technically says nothing about scroll creation, and as far as research goes, it explicitly doesn't change the underlying spell.  So this one is kind of in the DM's hands. - This (and the Alternate Spell Source feat below) is one of the few ways to get access to the Wu Jen's spell list, and other more obscure arcane lists.

Alternate Spell Source (Dragon 325 feat) - Similar to Southern Magician, but much more explicit in it's use.   

Several PrCs add spells to divine lists:
Hathran
Malconvoker
(more to add here)

Practical Guide to Prayerbook Expansion:
Adding spells to your prayerbook is mostly going to be limited by three things: 1. Money, 2. Availability, and 3. Time.  So, let's look at ways that we can minimize the impact of each one.

Money
So, now you've looked at the list of recommended spells and are going "how the %^&$ am I going to afford that?".  And, yeah, it's expensive being an archivist, let's just get that out of the way; be prepared to drop some cash.  First of all, craft as many scrolls as you can yourself.  The xp loss is laughable compared to the power increase you get from more spells and/or more wealth.  Craft them as archivist-only and (some skill)-only to reduce the base cost by 37%.  You'll still have to buy some full price most likely, but this should at least ease the cost considerably.  Secondly, if you have a DM that strictly enforces the spellbook scribing rules, that's going to be painful. It costs 25g for a 1st level scroll, it cost 100g to scribe into the spellbook.  So, at first, go easy on the scroll making/purchasing, until you can afford to get an Aureon's Spellshard or Boccob's Blessed Book.  Either of those will turn scribing costs from 100/level to 12.5/level.  Be sure to scribe all of your old spells into your new prayerbook (for free) and then sell the old one to recoup some of the loss.

Availability
But that money saved doesn't do much if you can't get access to the spells you need.  Thankfully, you only need to find someone who has access to the spell list you need, and they can provide the spell for you to craft the scroll.

Relevant section (DMG 215):

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"Certain requirements must be met in order for a character to create a magic item. These include feats, spells, and miscellaneous requirements such as level, alignment, and race or kind. The prerequisites for creation of an item are given immediately following the item’s caster level. A spell prerequisite may be provided by a character who has prepared the spell (or who knows the spell, in the case of a sorcerer or bard), or through the use of a spell completion or spell trigger magic item or a spell-like ability that produces the desired spell effect. For each day that passes in the creation process, the creator must expend one spell completion item (such as a scroll) or one charge from a spell trigger item (such as a wand), if either of those objects is used to supply a prerequisite. It is possible for more than one character to cooperate in the creation of an item, with each participant providing one or more of the prerequisites. In some cases, cooperation may even be necessary, such as if one character knows some of the spells necessary to create an item and another character knows the rest.

If two or more characters cooperate to create an item, they must agree among themselves who will be considered the creator for the purpose of determinations where the creator’s level must be known. (It’s generally sensible, although not mandatory, for the highest-level character involved to be considered the creator.) The character designated as the creator pays the XP required to make the item. Typically, a list of prerequisites includes one feat and one or more spells (or some other requirement in addition to the feat). When two spells at the end of a list are separated by “or,” one of those spells is required in addition to every other spell mentioned prior to the last two. For example, the prerequisites for a ring of three wishes are “Forge Ring, wish or miracle,” meaning that either wish or miracle is required as well as the Forge Ring feat."

So, you just need to find a source to supply the spells.  Now, the ideal method for this is access to a 12th+ level warlock who can emulate any divine spell in existence for the purpose of item creation.  It's completely worth taking Leadership just for that purpose.  But, this method isn't available until later, so what to do until then?  Well, you can get help from any other divine casters in the group, of course.  But if that's not an option, there are a few other tricks you can pull.  One of my favorites, is to planar bind an outsider with full spellcasting and making the deal for them to hang around for a few days making scrolls with you.  The first day, you're stuck with whatever they have listed as memorized, but after that, just have them prepare whatever spells you want to learn.  A completely safe task, very limited; it should even give a bonus to the charisma check.  (you can even fluff it with "I need this to smite the forces of evil, blah blah blah".  If spells are in really short supply, it's probably worth it even to buy a scroll of planar binding earlier than you could cast it, although obviously the risks are greater.  And that's an easy way to get access to the cleric list; the druid list is a bit harder though.  You can do it, but it requires using a spell line from Oriental Adventures called spirit ally.  It's like the planar ally line, except instead of an xp and gold cost, you exchange favors.  One of the options for calling with that line is a nymph, who has full druid spell casting as a 7th level druid.  Don't bother paying an NPC to cast for you to create scrolls though, you end up paying almost full scroll price + the xp. 

Also, Holt Warden + any Domain + domain substitution gives you access to a lot of domain spells (how many, is, of course up to your DM) and an excellent argument for not choosing a particular deity.

Time
The biggest pain in the ass for scribing scrolls and learning spells is the time, though.  For the scrolls, there are a few tricks to use - the Quill of Scribing from Complete Mage can scribe for you while you do other things.  Also, the time listed to craft a scroll is 1 day per 1000g - so what you want to do at lower levels, is make scrolls with several spells on it at once.  On the other hand, the rules for learning spells and scribing it into your spellbook suck.  (granted they are better than they were in 3.0, but still...)  Sadly, I don't know of anyway to speed that part of it up.

[Mooncrow]

Equipment

Armor

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Types:
Mithril Breastplate - get this as soon as you can.
Armor Spikes - enchant it with +1 defending and then cast Greater Magic Weapon on them for a nice +5 AC
Magic Vestments - with an hour/level duration, you can save a whole lot of money by keeping your actual armor enhancement as low as possible and boosting it with this spell (and you'll need the extra cash^^)
Bracers of Armor - most of the time, too expensive for what they offer. 
Enhancements
Called (MIC - 2000g) - no more worrying about being caught without your armor.
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:
Buckler - You don't have proficiency, but make it masterwork and it doesn't really matter.  And now you have a platform to toss a whole new suite of defenses on.
Shield Spikes - enchant it with +1 defending and then cast Greater Magic Weapon on them for a nice +5 AC
Enhancements
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
Animated (DMG +2): not 100% needed unless you're doing something that requires attacking with your off hand, but potentially useful.
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
Light Crossbow - this is the weapon for the back rank fighter; can fire once a round, decent range increment, no penalty on damage for low Str. 
Gauntlet - another target for the +1 defending Greater Magic Weapon combo
Morningstar - if, for some reason, you end up wanting to mix it up in melee (with Divine Power up, hopefully) this is a solid weapon to use.
Quarterstaff - another solid option, since you have access to druid spells to buff it up.  Once you have access to 6th level spells for spellstaff, this is your weapon of choice.
Enhancements
Warning (MIC +1) - a +5 insight bonus to initiative?  Yes, please.  Add it on to the gauntlets so it's always on.
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 Armor
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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Most likely will be taken up with armor, if not here are a couple other options:
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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Crystal Mask of Languages (MIC 2500g) - speak up to 5 additional languages - this is handy to have for the more obscure summons you might want. 
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 taht 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) - gives you a +3 circumstance bonus on all Cha checks - great for planar binding or Malconvoker builds.
Headband of Intellect (DMG 4000-36,000g) - add this on to another item with the MIC rules.

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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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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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) - extra turning charges for more DMM fun
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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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.

Relic

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Scrolls of Uncertain Provenance (MIC 8000g) - For LG, LN, LE, and N characters, they give a constant +5 competence bonus on all knowledge checks.  The relic power is pretty terrible though, making the price a touch high.

Other

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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.
Nightstick (LM 7500g) - 4 extra turning attempts; even if you don't try to the "bag full of nightsticks" trick, it's still a very good item.
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
Tome of Worldy Memory (MIC 1500g) - 3/day gain a +5 competence bonus on a knowledge check.
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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Frog God's Fane (CS) - bonus knowledge skill focus
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]

When multi-classing with an archivist, there are a few common opt-out points - 1, 8 and 11.
At first level, you really have the core of what makes the archivist great, the spell list.  If you're not interested in anything else, get out as soon as you qualify for something else.
By 8th, you have the best party-wide Dark Knowledges and enough daily uses to be fine.  This is probably the most common point to leave.
11th level isn't bad either, you get a bonus feat and the very nice no-save stun ability of Dread Secret.  After 11 though, there's nothing worth hanging around for. 

Single level dips
Binder^ToM - necessary if you're going for Anima Mage (Divine Variant) and it has some interesting abilities on it's own. 

Cloistered Cleric^UA - if you're really hot and heavy into DMM, this will give an extra pool of turning/rebuking attempts.  That + the 3 domain powers makes it one of the few classes I would consider almost worth dipping.

Dread Necromancer^HoH - if you need some arcane spellcasting for a PrC (like dweomerkeeper), it can help to grab one that comes with DMM fuel. 

Prestige Classes 

Sacred Exorcist^CD - the entry into the beauty of DMM.  Requires a good alignment, and the ability to cast dismissal or dispel evil.  Hit dice bump up to d8, fort save drops to poor.  Earliest Entry - 8

Holt Warden^CC - if you want to mess around with domains, I highly recommend this class.  At first level, you gain bonus domain spell slots just as a cleric does for the Plant Domain.  If your DM allows other rebuke/turning to fuel DMM, grab the second level as well for the rebuke plants ability.  After that, it's just a handful of druid abilities and some divination until level 7, where you get the ability to allow every divine caster around you, as well as yourself, to get 1d4 spell levels per day back after casting them.  Earliest Entry - 6

Moonspeaker^RoE - a good summoning PrC, though you do have to be a shifter to qualify.  The first four levels give you free Augment Summoning, Extended Summoning, and an expanded SNA list, including some nice utility.  But the real interesting ability comes at 5th level, where you gain Wild Shape, making this one of the few ways for a non-druid to qualify for Planar Shepard.  Earliest Entry - 9

Planar Shepard^FoE - even with delayed entry, this class is still disgustingly good.  You can't pull off some off some of the usual tricks, like Efreeti wild shape, but you can still get planar bubble for some 10 rounds for every 1 of the enemy silliness.  Earliest Entry - 15

Thaumaturgist^DMG - Ok, back to classes that I would really play; thaumaturgist is really nice, over four levels it gives you Augment Summoning, Extended Summoning, and best of all, Contingent Conjuration.  Take 10 minutes between battles to set it up to trigger on "when I'm attacked" or something similar, and open every fight with an extra summoning.  The fifth level gives you a planar cohort, which honestly, I've never really looked at.  Earliest Entry - 8

Malconvoker^CS - another summoner PrC, you lose a level of casting on this one, but gain all sorts of nice abilities when summoning evil creatures.  The first 5 levels mostly boost the Summon Monster line, with the level 5 ability allowing you to summon in an extra copy of evil creatures.  The last four levels mostly boost the Planar Binding line (which are added into your prayerbook automatically)  For more info, check out Treantmonk20's Mastering the Malconvoker.  Earliest Entry - 6

Anima Mage (divine adaptation)^ToM - One of the very few dual casting classes that are worth anything. You only need one level of Binder and one feat, so you don't fall far behind in your casting. In exchange, you gain a host of really useful abilities (really, too many to list here, check out Sobolev's guide for more Binder info.  But, along with the Binder abilities, you also get extra spell slots, and starting at 5th level, you can spontaneously add any metamagic you know to a spell on the fly.  Earliest Entry - 5  (you will need to clear the divine adaptation with your DM first though)

Sovereign Speaker^FoE - Jealous of the clerics domain abilities?  Then pick up this class and get a bonus domain every level.  You lose out on two caster levels if you take all 10 levels (at 1 and 6) so feel free to swap out at 5.  For best results, be sure and take at least one level in Holt Warden before you enter this class.  Earliest Entry - 6 (this requires a little trickery though - you'll either need to dip a level of some flavor of cleric, or do an early entry into the Church Inquisitor PrC to qualify) 

Dweomerkeeper^{CD (web)} - a full casting PrC - it adds more spontaneous casting, allows you to cast spells as SLAs, and the capstone reduces the cost of all metamagic by 1.  Incredible class for the non-summoner. 

Contemplative^CD - a full casting PrC that a one level dip in will get you a bonus domain (any available by deity or alignment) and immunity to disease.  If you stay in, you get a second bonus domain at 6th, and immunities to poison and aging, and also gets SR of class level +15 and DR 10/magic.  Not terrible as a one level dip, but I think there are better choices.  Earliest Entry - 11

Mystic Wanderer^MoF - It's a bummer that with all the amazing buffs and spells that you have access to, you still can't get a familiar to share it with... oh wait, yes you can!   Mystic Wander is a full casting PrC that gives you a familiar at second level.  The entrance requirements are kind of crappy (Iron Will, and some wasted skill points) but easy, and when you're not wearing armor, you get a sacred bonus to AC equal to your charisma bonus.  The rest of the class is kind of shitty though (centers on potion making and gem magic, with some minor SLAs), grab the familiar and get out.  Earliest Entry - 6

Knight of the Raven - an interesting option for the more gish oriented archivist.  This is a 9/10 casting class (lost level is 1st) with full BAB, grants undead turning, the Sun Domain (unlike other Domain adding PrCs, this one specifically adds the spells to your normal spells known if you don't have domain spell slots), and a familiar-like companion.  Earliest Entry - 9 (for the straight archivist; you need +4 BAB to qualify)


More to come...

[Mooncrow]

The Summoner: Archivist 7/Sacred Exorcist 1/Thaumaturgist 4/Archivist +1/Holt Warden 1/Contemplative 1/Archivist +3/Paragnostic Apostle 2

The Malconvoker:  Archivist 5/Malconvoker 5/Thuamaturgist 4/Archivist +6

The Dweomerkeeper: Cloistered Cleric 1 (Rebuke Dragon ACF^DM)/Archivist 5/Dweomerkeeper 2/Sacred Exorcist 1/Dweomerkeeper +8/Anything 3

"The JaronK Special":  Binder 1/Archivist 3/Anima Mage 10/Tainted Sorcerer 1/Tenebrous Apostate 5



caveat: I almost always play summoners, so my knowledge of non-summoner builds is mostly theoretical, or from watching other players in my group.

[Mooncrow]

Credits:

Thanks to Phaxi for the original guide; I know it helped me out the first time I ran an archivist.  Hopefully my guide can do the same. 
Thanks to After Crescent for the formatting of his excellent cleric guide; it was a big help in organizing mine.
Colm_l and DM_Awaken_Golem for their work on the lowest level spell lists

Everyone that originally contributed to the old archivist threads both here and on the WotC boards.
Everyone that posts in this thread - your comments are much appreciated!

Still to do:
More sample builds and tactics
Fleshing out the spell lists, and ranking spells
Finishing the equipment section
Guide to Scroll making
Also, races, feats, and 100 other things, I'm sure

Most importantly, my complete list of divine spells by level and source; but that is going to continue to be on the back burner for a little bit.

[Mooncrow]

Build #1 - The Summoner (non-Malconvoker)

Archivist 7/Sacred Exorcist 1/Thaumaturgist 4/Archivist +1/Holt Warden 1/Contemplative 1/Archivist +3/Paragnostic Apostle 2

Race: Human
Feats
Human - Academic Priest
1st - Spell Focus: Conjuration
3rd - Rapid Spell
6th - Twin Spell
9th - Divine Metamagic: Twin Spell
12th - Metamagic School Focus: Conjuration
15th - Rashemi Elemental Summoning
Archivist Bonus - Quicken Spell
18th - Divine Metamagic Quicken

Playing:
One of the nice things about a summoner build is that it takes relatively few spells to make work, and having the options of both the summon monster and the summon nature's ally lines makes the archivist summoner a powerful, versatile force even before adding in the other powers of the build.

Level 1-3: the painful levels.  Break out the light crossbow and stay out of the way.  Use Dark Knowledge and party-wide buffs like bless to make your teammates more effective, and use battlefield controls like entangle and sleep to divide and conquer.
4-8: by this point, your summons stick around long enough to be useful.  For now, mostly stick to the SNA lines, since it offers the superior combatants, and the summon monster spells don't have anything to make up for their poorer choices. 
9-13: this is where the build really comes online.  With Twin Spell and then Contingent Conjuration (I like to just key mine to a command phrase) you can open combat with up to three summons in the first round.  Pouncers really become a strong option with Dark Knowledge: Foe adding 2-3d6 to every attack's damage.  And with buffs like animal growth available, you can really sit back and let your summons take care of the combat, while you focus on battlefield control.
14-18: Now we start to add a little more diversity into the mix.  By picking up domain spell slots and an actual domain, now we can play shenanigans with spells like substitute domain and anyspell to diversify the options.  Summoning-wise, elementals begin to really shine for combat, and the summon monster line starts to bring really useful SLA's to the table. 
19+: at this point, your archivist should really be able to do anything.

[Mooncrow]

Build #2 The Malconvoker

Archivist 5/Malconvoker 5/Thuamaturgist 4/Archivist +6

Race: Human
Feats
Human: Academic Priest
1st: Spell Focus: Conjuration
3rd: Augment Summoning (if retraining is allowed, retrain this after getting it from Thaumaturgist)
6th: Practiced Spellcaster
9th: Rapid Spell
12th: Metamagic School Focus: Conjuration
12th: Retrain Augment -> Leadership
15th: Summon Elemental (Reserve)
18th: Planar Touchstone
Archivist Bonus: Sudden Maximize

This is my usual build when I can't play with divine metamagic.  It plays very similarly to Build #1, but you have to be more careful with money, since you rely more on magic items to apply non-level adjusting metamagic.

[Mooncrow]

Build #3 - The Dweomerkeeper

Cloistered Cleric 1 (Rebuke Dragon ACF^DM)/Archivist 5/Dweomerkeeper 2/Sacred Exorcist 1/Dweomerkeeper +8/Anything 3

Race: Human
Domains: Magic, Planning
Feats:
Human: Practiced Spellcaster
1st: Academic Priest
3rd: Southern Magician
6th: Persist Spell, Travel Devotion
9th: DMM Persist
12th: Twin Spell
15th: DMM Twin Spell
18th: Quicken Spell

The master of divine metamagics, you're all about persisting insanely powerful buffs, and using potent Save or Lose spells.  Cast them as SLAs against enemies with SR, or Twin Spell against anyone else.  With flaws you can grab DMM persist early on, and be a powerhouse from the word "go"  - thanks to OblivionSmurf83 for the build change suggestions.