Arsenic & Old Lace: The Poison Handbook

[Libertad]

Credit goes to Akalsaris

Arsenic & Old Lace: The Poison Handbook

And we're all out of lace

2 Links:

SRD Links:

Poison
Poisons
Fabricate
Artifice Domain
Jungle Halflings

The Big Chart of Poisons on GitP: A chart of many poisons, however it is also out of date and incomplete.  Useful for quick comparisons, however.
Trouserfang Dwarf Build: A build that uses poison for hilarious results!
Minor Creation and You: Goes over some of the creative uses for Minor Creation.
The Avenger PRC: A non-evil Assassin variant.
Craft (Poison-making) for money-making: Using Salvo from C. Scoundrel to make money by abusing Craft (Poison-making)'s faster craft times.

For fun from the Order of the Stick:

High-level wizard taken out by Dragon Bile Poison!
Oh yeah, Black Lotus poison- that's the good stuff!

COMPLETE POISON-USING BUILDS from various Iron Chef challenges:

Ilphaid Shiiralice, by T.G. Oskar 
LE Male Drow Rogue 3/Monk 2/Master of Masks 1/Assassin 8/Child of Night 4.  An elegant build that combines stealth, sneak attack, death attack, and poison's ability damage to great effect.  Between Increase Virulence, Venomous Strike and Aleval School, his poisons have +2 to DC and -4 to saves, which then benefit his Death Attack, especially with Con-damaging poisons.

Ruszel, by Draz74.
LE Human Factotum 8/Beastmaster 1/Assassin 1/Snakelord 7/Uncanny Trickster 3.  A build that fills the damage-dealer and scout/high-skills roles in a party. Ruszel has access to poisons through summoned snakes (easily transformed into gargantuan-sized snakes!), purchased and trained snakes, and a Druid 16 snake animal companion, as well as his own poisons from Snakelord's Wild Aspect.  His specialty is assigning constrictor snakes to grapple opponents, making the foes flat-footed for him to then sneak attack.

Sway, by WinWin. 
CE Yuan-ti Pureblood, 4 Monstrous HD/Bard 2/Snake Lord 10/Soul Eater 1/Cloaked Dancer 3.  Just as a sidenote, I love this character.  Sway is a "party face" who also fills the crowd control and damage-dealer roles quite effectively.  She has a natural poison, access to poisons through summoned and charmed snakes, and also drains levels with every natural attack through Soul Eater.  Her animal companion is a Sailsnake, which flies and spits blinding venom in a 20ft cone.  Also take note of Amphisbaena, her quintessential poison-user's weapon!

Hugo Clopin, by Akal-Saris.
NE Strongheart Halfling Beguiler 5/Mindbender 1/Psionic Assassin 1/Psibond Agent 10/Magical Trickster 3.  See post #174 for the build.  Hugo is near-undetectable and mentally controls minions and opponents at-will from 100ft away, and uses poisons to weaken foes' saves, poison his minions' weapons, and to dispose of dominated opponents in a classy way.

Danny and Rusty, by FishAreWet.  Changeling Rogue 1/ Psion (Shaper) 7/ Black Dog 2/ Psibond 8 / Ghost 2.  See post #187 for build.  The build ingeniously uses true mind switch and psionics to both create poisons and the minions to deliver them.

Jorath, the Hand of Annihilation, by Akal-Saris. 
LE Human Paladin of Tyranny 4/Hexblade 4/Blackguard 7/Entropomancer 5.  See Post #116.  A straightforward tank build that debuffs saving throws of nearby opponents by about -8 to -14, so that opponents are almost guaranteed to fail their saving throws against poisons.

Nicolo Egidi, by Amphetyron.
LE Halfling Rogue 1/Hexblade 4/Black Dog 5/Green Star Adept 10.  See Post #155.  A jack-of-all-trades build that is a decent tank and debuffer as well.  With empower poisons, dhurinda's touch, and poison spell, he can apply poisons in several different ways (including a slam attack), and he has a wide array of resistances and armor from green star adept. 

Aesc Duan Dee, by Zaq.
Chaotic Neutral Uurkrau Illumian Rogue/Binder/Warlock/Ranger/Swordsage/Warblade/Trapsmith/Disciple of Thrym/Sand Shaper/Ardent Dilettante.   Part 1 (story) and Part 2 (crunch).  The most complicated build listed here, Aesc primarily fills the scout and damage roles, but between vestiges, spell-casting, maneuvers, and psionic powers, he is really quite the jack-of-all-trades.  He creates poisons with Minor Psionic Creation and delivers them through touch spells laced with Poison Spell.  Interestingly enough, Aesc is not immune to poisons, but instead relies on the Naberius vestige to heal any ability damage taken from accidentally exposing himself to poisons.

3. Poison: How does it work?

You can poison a weapon or natural weapon as a standard action that provokes an attack of opportunity, and you have a 5% chance when applying it to poison yourself (still getting a save).  You also might poison yourself if you roll a 1 in combat with a poisoned weapon and then fail a DC 15 reflex save.

You can avoid all of that trouble by getting poison use as a class or racial ability, or through taking the Master of Poisons feat, or through immunity to the poisons you use, or through having very high fortitude and reflex saves.

In general, you want a poison that complements your party strategy.  You also need a steady supply of cheap poison, either through magically creating it or from an item/spell/friendly animal.  Most poison users are good de-buffers, since status effects such as shaken and sickened lower saving throws, which make poisons more effective, and poisons that damage con/dex/wis lower saving throws, making debuffs and save-or-die abilities more effective, which leads to a very effective cycle between poisons, debuffs, and crowd control.

Low levels (1-5): This is when poisons are best.  Crowd control is often the key to low level encounters, so those DC 14 blinding, sleep, or nauseating poisons are the best choice here.  Crafting poisons will probably take a steady stream of gold out of your income at this point, especially if you lack the raw materials.

Mid levels (6-12): At this point you really need to look for the high save DC poisons to maintain their effectiveness, or otherwise focus on a high number of attacks per round with poisoned weapons.  At this level most of the crowd control poison DCs are too low, so its better to focus on ability damage.   However, most magical ways to create poisons for free are also available at this point.

Higher levels (13+): By higher levels a lot of creatures are going to easily make the fortitude saves for any DC under 20, and many opponents at these levels are immune to poison.  However, the relative cost of poisons declines considerably with higher WBL, so you can also use poisons more liberally than before. 

How important are poisons?
One of the basic things to understand is that poison use has a high initial return, but a low return for more investment.  For example, spending 8 skill ranks and a feat to use and make poisons provides a lot of power, but spending 23 skill ranks and five feats will generally only make your poisons moderately better. 

So it's important to understand the opportunity cost of poison-related feats and abilities - even if you use poisons in every fight, often power attack or quicken spell will be a better feat choice than Poison Master, for example.  Likewise, if I were making a poison-using wizard, I would take Red Wizard or Incantatrix over the Alchemical Savant, because the rewards are greater over time. 

For example, if you're a 9th level druid and have 4-5 skill ranks to spare, investing in poisons is simply good thinking.  Almost any non-good wizard who is 7th level should learn minor creation.  Anyone playing a warforged, undead, or dragonwrought kobold also can use poisons without giving up anything for the ability.

To sum up: I don't recommend specializing in poisons unless you want to be thematic.  Poisons - like levels in fighter - are best as a small dip to increase the power of many builds, but generally shouldn't be the main focus of a build.

Poison: its Pros and Cons:

Pro:
High return for low feat/skill/class investment
Easy way to get ability damage or crowd control effects
Synergizes well with Save-or-Die's (Disintegrate, Death Attack, etc.)
Extraordinary ability, so it functions in an AMF.
Good synergy with many classes and different roles in combat.

Con:
Evil.  Many PCs won't be able to use poisons because of their alignment.  You might be able to use sleep and paralyzing poisons with good characters, even if your DM is strict about alignments.
Undead, devils, demons, elementals, plants, constructs, and oozes are immune.  There are specialized poisons that can affect undead, devils, and demons, but they are expensive.
Expensive to use most poisons without crafting magically. 
Often requires a skill investment.
Low availability without prior preparation.

[Libertad]

Skills:
Craft (Alchemy): alchemists can make poison at a -4 to their check.  This also lets your character make alchemical substances, drugs from the BoVD, and positoxins from Libris Mortis.
Craft (Poison-making): The requirement for some poison-specific feats.  Unlike other Craft feats, Craft (Poison-making) progress is measured in gold rather than silver, so the process is faster.
Handle Animal: According to Drow of the Underdark, it's a DC 15 Handle Animal check to convince a vermin with the Bestow Venom trick to give enough poison for a single dose, and then a DC 15 Craft check to distill that material into a usable poison.  Teaching the trick requires the Vermin Trainer feat or a similar ability, such as the vermin keeper prestige class.  It's reasonable to assume that animals can learn a similar trick as well if the DM is willing to create such a homebrew feat (or allow Wild Empathy to qualify).  It's easier to make two DC 15 checks than it is to make most difficult poison-making checks.

Poison: Tricks and Tips

Weapons - Injury and Contact Poisons
Contact and injury poison can be applied to a weapon as a standard action, and it lasts until the weapon hits something.  Injury poison is almost always cheaper and easier to make than contact poison.

In general, the best use is probably poisoned arrows or thrown weapons, since then every attack will be poisoned without wasting actions in combat.  Color your arrow shafts and fletches to easily identify your poisons.  Try to retrieve them after a fight if cost is an issue. 

Inhaled poisons
These are a 10ft ranged attack, not a ranged touch attack.  You can attack a floor or table easily enough however.  The Launch Object cantrip is spectacular for giving a much longer range on this attack: 110 feet at a minimum.  Inhaled poisons almost always are harder to make and have a lower save DC than their counterparts, but they are best against groups of enemies or foes whose normal AC is too high to hit normally (in which case a Dex-damaging inhaled poison might be a good idea).

Ingested poisons
A mister (DoTU equipment) can spray an ingested poison into somebody's face, but in general these are not usable in combat.  But combined with charm spells, diplomacy, or simple back-stabbing (figuratively!), they can be effective.  They are usually much easier to create and have weaker initial effects, but stronger secondary effects.

Secondary effects
Remember that a creature must save against the secondary effect even if it succeeds the first one.  Most combats in D&D don't run for 10 rounds, so I always give priority to the primary effect over the secondary.  The Virulent enhancement (DoTU) reduces the wait to 5 rounds for contact and injury poisons, however, while the Lolth's Caress feat can force the secondary effect as a standard action.  In either of those cases, it becomes more valuable.

Ways to get poisons

The major balancing point against poison is its cost.  Wyvern venom might be awesome, but at 3,000 gold a pop, that's the same cost as a young wyvern!  Therefore the first thing any poison user needs to do is find a reliable source of poison. Below are some ideas to get you started.

Make it yourself: Progress is tracked in gold rather than silver pieces for the checks, and if you have easy access to the raw materials then the cost is only 1/6th of the base price.

Easy base prices chart at 1/6th cost:

(click to show/hide)

40g: 6.6g to make
100 gold: 16.6g to make
200g: 33.3g to make
300g: 50g to make
500g: 83.3g to make
1,000g: 166.6g to make
2,000g: 333.3g to make
3,000g: 500g to make

Animals & Vermin: one of the most intuitive ways to get the base materials for poisons is to get them from animal companions, pets, etc.

According to Drow of the Underdark, it's a DC 15 Handle Animal check to get a vermin to bestow its venom into a container, and then a DC 15 Craft (Poisonmaking) check to distill the poison.  As a DM, I would require 1/6th of the cost of the poison to be paid as part of the DC 15 Craft (Poisonmaking) check to distill the poison.  It doesn't state the time required or the amount of poison that can be distilled per day, but one dose per day is a reasonable assumption.  As noted earlier, it requires the Vermin Handler feat to do this, or a related ability - presumably Wild Empathy or Vermin Empathy would also work for this.

Minor/Major Creation & Fabricate: make tons of plant-based poisons yourself for free (30,000 doses at the minimum caster level!).  Unfortunately it typically requires a 7th-9th level spellcaster.  The exception is the psion (shaper), which can use minor creation at 1st level. 

Find it: try to disable traps and such that have poisons, or get it from dead poisonous opponents.  If you make a habit of checking for poisons, most DMs will get the hint pretty soon. 

Black market: since poisons are generally found in the hands of the criminal underworld, one good way to get them is through role-playing.  Try and perform mini-quests for assassins' guilds, or strike a bargain with the local godfather.  Can potentially be cheaper and more fun than simply purchasing poisons. 

Locate Object: this simple spell can help you find some components for your poisons during downtime.  Casting it while traveling, for example, can lead to the DM having you discover some new poisonous plants in the forest or dungeon.  In Pathfinder, casting Detect Poison every few minutes is also an option, since you have unlimited cantrip casting.

Survival: same as Locate Object, this can lead to some cheap and readily available poisons in an outdoor campaign.  There is no check listed for scavenging poisons, but DC 15 would be a reasonable house-rule.

Ways to make poisons last longer

Poison Spell: this feat from Drow of the Underdark lets a poison apply to your touch spells - and Chill Touch lasts for up to 5 attacks, therefore spreading the dosage out over several rounds. 

Toxic Enhancement: This +1 weapon enhancement from DoTU makes a poison last for 2 successful hits instead of one.  Just what the doctor ordered!

[Libertad]

5.  Races:

Here are races that are naturally good at poisons.  Poison use as a base ability really is not as hot an ability as it first appears, since the Master of Poisons feat is superior to it.
Human: An extra skill and a feat - that's four ranks in Craft (Poison-making) and the Master of Poisons feat right there!  The best race possible, as usual.
Kobold (Dragonwrought): immunity to paralysis and sleep lets dragonwrought kobolds use some poisons without having poison use, good for casters who were already planning on being a Dragonwrought Kobold.  There are several poisons in Serpent Kingdoms that hurt enemies while simultaneously buffing kobolds, making kobolds a blue choice!
Wild dwarves (Races of Faerun): small-sized humanoids with FR 5, the same abilities as normal dwarves, and have poison use as a racial ability but lack the craft skill bonuses.
Jungle Halflings (Unearthed Arcana): Get poison use as a racial ability.
Marrulurk (Sandstorm): Jackal!  Jackal!  It's a jackal!  A 3HD Monstrous Humanoid with +1 LA, Marrulurks get a Death Attack as a racial ability, as well as 2d6 Sneak Attack and poison use.  A good race, even if it pigeon-holes you into being an assassin-type character.
Half-Drow (DoTU, PGtF, RoD): The goodness of drow without the +2 LA.  There are a lot of drow-related poison abilities, and drow cities are the most likely place in most campaigns to find components for poisons readily available. 
Gnome, Tinker (DLCS): With +2 to all Craft skills and +2 Int, this is a natural fit for a wizard or artificer. (Thanks Telehax!)
Undead (Libris Mortis): immunity to poisons as a racial ability, plus you can craft poisons day and night without rest.
Warforged (EBCS): immunity to poisons as a racial ability, plus you can craft day and night without rest.
Thri-Kreen (Expanded Psionics Handbook, Shining South): Good for a lot of melee class builds like Dervish and whatnot, the race comes with its own poison.

6. Classes:

You should choose a class based on your primary role in the party, and then consider how poisons fit into that character idea.  A ninja gets poison use for free, for example, but I'd go with a rogue in the party over a ninja any day.  The ratings provided, however, reflect how well the class is able to create and make use of poisons. 
Ardent (C. Psi): Can cast Psionic Minor Creation at 1st level, making him a capable low-level poison crafter.  The Ardent is wisdom-based, so the psion will still be slightly better at crafting.  A Divine Mind can also pull this off starting at 4th.  Thanks awaken DM golem!
Artificer (EBCS): Most poison-related spells are low level, so crafting wands/staves for them is cheap.  The artificer is also likely to make use of poisoned weapons at low levels.  Since warforged are good artificers and are naturally immune to poisons, it's a natural fit - and many feats that reduce crafting cost & time also affect Craft (Poison)!
Bard (Drow): Gains poison use as a class ability at 1st level in place of bardic lore.  I believe Dark Sun bards also have some poison-related abilities. 
Ninja(Water) (C. Adv.) : Dragon Magazine 354 gives ninjas the option to create Obscuring Mist as a swift action in place of invisibility, and at 8th the ninja can lace the mist with a contact or inhaled poison at -2 DC and immunity to her inhaled poisons, while at 10th it becomes a Solid Fog spell that affects everyone except you. Also gains poison use as a class ability at 3rd level.  Overall a niche class compared to the rogue or factotum for the same roles, but an interesting one. Thanks for the suggestion, Shortstraw!
Binder: Malphas grants Poison Use starting at 3rd level, along with the ever-useful Sudden Strike and invisibility.  Focolor and Chupoclops lowers nearby opponents' saves by 2.  Karsus lets you use wands of Minor Creation (and several vestiges let you use dorjes of psionic minor creation).  Eurynome lets you befriend animals with poisons. Astaroth gives bonuses to Craft (Poison) and lets you make magic items like a +1 Assassination, Toxic Dagger.
Cleric: The Artifice domain grants +4 to craft checks and all of the wonderful creation spells (fabricate, minor creation, true creation).  The Lolth's Caress divine feat is notable for speeding up the secondary effects of poisons - as a standard action, you force an opponent to make the secondary save.  Like most things, the cleric is ambivalently good at using poisons without even trying.
Druid: one of the best poison-using core classes.  Immunity to poisons starting at 9th level, animal companions that can provide poisons, and a wide range of poison-related spells and feats.  Surreal recommends turning into a poisonous animal or plant and providing your own venom - particularly the Elder Viper Tree from Expedition to the Demonweb Pits. One level of contemplative can nab the Artifice domain for the poison creation spells as well.
Duskblade (PHB II): a top choice in my opinion, especially with the Poison Spell feat from DoTU.  At 13th level, the touch spell channeled hits every opponent in a full attack action - and the poison attached to the spell should hit each opponent as well.  Additionally, the damage from the poison can help the duskblade overcome fortitude saves for spells like ghoul touch and toxic weapon.  Taking Arcane Disciple for the Artifice domain will give Minor Creation and Fabricate.
Factotum (Dungeonscape): The factotum is especially good at crafting, and can use fabricate and minor creation for cheap poisons, which he is likely to use or give to allies.  The Master of Poisons feat is probably all that your average factotum needs to be a competent poisoner.  Cunning Insight might even add your Int to poison damage, depending on your reading of it. (Thanks JaronK!)
Psion (Shaper): Gets psionic minor creation at 1st level, letting him pull off creating plant-based poisons at 1st level.  Good as an alternative to wizard, especially at low levels.
Rogue: very flavorful, and there are a few sneak attack-based poison abilities and PrCs.  Drow rogues can exchange their trap-finding ability for poison use.
Wizard: At low levels a wizard isn't great at poisoning, but everything changes at 7th-9th levels, when they gain the ability to magically fabricate ludicrous amounts of poisons.  Most wizards won't use poisons themselves except in very specialized builds, but they can give them to summoned/called/animated creatures and party members.

7. Prestige Classes:

Assassin (DMG): Grants poison use at 1st level.  Con-draining poisons can make death attacks vastly more effective as well, so there is a natural synergy.  There is a non-evil variant, the Avenger, in the links section.  Core.
Psionic Assassin (Secrets of Sarlona): As the assassin, but with power points.  Can easily UPD dorjes of psionic minor creation.
Alchemist Savant (MoE): Gains poison use at 1st level, plus full spell-casting and nifty potion effects.
Blackguard (DMG): Grants poison use at 1st level, as well as Aura of Despair to reduce saving throws by -2.  Their spell list includes Poison.  Also the only class on this list with +1 BAB.  Core.
Black Dog (Dragonmarked): This is a 5-level roguish PrC that centers around using dragonmarks to create poisons, and has a death attack that stacks with assassin levels.  The 3rd level ability gives a +2 DC increase to poisons, and the 4th level ability allows you to empower a dose of poison for a few minutes - a unique ability.
Dread Fang of Lolth (DoTU): A 10-level fighter/rogue PrC that grants poison use at 2nd level, and increases poison save DC's by 2 at 6th level.  The capstone ability to act fully in a surprise round is good. 
Master Trapfinder (Dungeonscape): Gets Fabricate as a spell.  Filling a room with poisoned bolt traps and the like is fun.  Amazing for a dedicated trapfinder. 
Poisonmaster (Dark Sun, athas.org): This is a 10-level roguish PrC that is entirely poison-focused. You can apply each dose twice, and by spending more on poisons, you can apply empower, maximize, and quicken (secondary 1 round later) to poisons. Also has all good saves, permanent Mindblank, and some minor DR. Note that athas.org is WOTC-legal, even though it's created by a second party.
Scorpion Heritor (Sandstorm): A PrC for rogues, this gives various scorpion-related abilities, including venom at 5th level.  8+int skills and the same amount of sneak attack damage, so it won't interfere with the skill-monkey role.
Zhentarim Skymage (Lords of Darkness): the first level in this full spell-casting class gets a flying mount dependent on your charisma.  Choice picks include wyverns and devils.  No CL loss.
Heir of Siberys (EBCS): Choosing the Mark of Making grants True Creation as a SLA, meaning it does not require material components or experience.  The errata corrects this, however.
[/list]

[Libertad]

8. Feats:

General

Master of Poisons (DoTU): gain poison use, and apply poisons as a swift action without poisoning yourself or provoking AOO's.  Priceless.
Poison Expert (CS): Raises the DC of a single type of poison (ingested, contact, inhaled, or injury) by 1.
Poison Master (CS): Requires Poison Expert. Choose a type of poison (Injury, etc.), and add +1 to the dice effect for the initial and secondary effects.  Good for a focused poison user.
Poison Specialization (Dragon 303 pg69) Prereq: Craft (poisonmaking) 5+ ranks.  Benefit: Whenever you create a poison of the chosen type, the Fortitude DC to resist the poison's effects increases by +2.
Poison Healer (FC I): You heal damage equal to your constitution each time you make a fortitude save against poison.  Check out the Trouserfang Dwarf link for some fun with it.  If your DM agrees that alcohol is a poison, get ready for fun drunken healing!
Favored & Special Dispensation (Cityscape): Special Dispensation lets you use items banned in a city, such as poison.  Favored is a weak pre-req feat, but Favored in House from the EBCS can also be substituted in its place. 
Animal Devotion (CC): Grants you a poisonous bite attack - plus other awesome abilities.  I'd use the bite during downtime to poison my weapons, then use the feat in combat to fly.
Hidden Talent (Expanded Psionics Pg. 67): This is a more high-powered variant of the Wild Talent feat that grants a single 1st level power 2/day.  Use it to take Psionic Minor Creation.  Thanks Havoc4 and Tomtomcat!
Lolth's Caress (DotU): A divine feat that lets you spend a standard action to force the secondary effects of a poison on nearby poisoned opponents.  Great, especially with inhaled poisons or if you have poisonous vermin helping you spread the pain.
Poison Spell (DoTU): This feat applies a poison to your touch spells.  It does come with one significant drawback (and, most likely, largely unintended), however: the poison becomes a material component for your spell, so duskblades will have to use one handed weapons without a way to avoid that; and poisons created through minor creation cannot be used as spell components, so you'll have to use mundane poisons with this feat.
Leadership: You can use it to get a cohort with the ability to create poison (a wyvern, wizard, etc), and have your followers work as secret poisoner cells in your hidden fortress.  As broken as always if you're willing to do the book-keeping required.
Wild Cohort: Use it to gain a animal companion to provide the raw materials for poisons.  I think it'd be especially worth it at low levels for a rogue as a poison dispenser and flanking buddy.  Thanks Prime32!

Crafting
Skill Focus (Poison-making): Useful only for low-level followers - you have better things to spend feats on, like improved initiative and feats that help in combat.
Apprentice (Craftsman) feat (DMG II): Appraise & Knowledge (arch & eng) become class skills.  Gain two skill points for those two skills.  +2 competence all Craft.  10% discount on raw materials for ALL Craft skills & item creation feats.  Probably blue for artificers and some wizards, as well as a feat for low level followers.  Note that Knowledge (arch & eng) has applications with Major Creation and Fabricate as well, and since this feat eventually turns into Mentor (Leadership Lite), it will be useful later on as well.  Thanks to Cavalry Medic for this and other crafting feat suggestions!
Mercantile Background (FRCS) - start with extra money that could be spent on poison, or that poison lab.  Good in a 1-shot game or on a follower.
Exceptional Artisan (EBCS) – [item creation feat] -25% time for *any* crafting.  Like Apprentice (Craftsman) this is great for a dedicated crafter, but probably not worth it otherwise.
Extraordinary Artisan (EBCS) – [item creation feat] -25% gp for any crafting
Mark of Making (EBCS): the lesser and greater feats grant minor creation and fabricate, letting any class pull off wizard shenanigans with poisons.  Heavy feat investment though.
Vermin Keeper (DoTU): Vermin-based poisons are decent but not too exciting - probably not worth it unless you were actually going to be a nature-based drow in the first place.  But at least the poisons you can make will be dirt cheap!

Sneak Attack
Venomous Strike (DoTU): Requires 2d6 sneak attack.  Sacrifice 1d6 sneak attack damage for +2 to the DC of your poison.
Sickening Strike (DoTU): Requires 2d6 sneak attack.  Sacrifice 1d6 sneak attack to make your opponent sickened (-2 to saves).
Terrifying Strike (DoTU): Requires 2d6 sneak attack.  Sacrifice 1d6 sneak attack to make your opponent shaken (-2 to saves).

Natural Poisons
Ability Focus (Poison): for creatures with their own poison attacks.
Virulent Poison (Savage Species): requires a poison attack as a special ability, but adds +2 to that poison's DC.
Deadly Poison (Savage Species): requires Virulent Poison, but doubles the secondary ability damage dealt by your natural poison.  Combined with Poison Master and Lolth's Caress, this could get brutal quickly.
Venom's Gift (CC) & Serpent's Venom (CD): wild feats to gain poisonous attacks.  Like most wild feats, these don't last long enough to be worth taking for most characters.

9. Animal companions:
1st:
Snake, Medium Viper: a pretty weak choice.
Sea Snake, Medium (Stormwrack) also weak, but slightly better with +2 to the DC of the bite.
Stingray (Stormwrack): the poison is quite excellent (DC 12 or nauseated for 1d4 hours, on a successful save sickened for 1d6 rounds), so this is a decent low-level companion for an aquatic game or for a druid that takes it during downtime to get poisons, and uses another companion while adventuring. 
Swindlespitter (MMIII): This is a dinosaur with a blinding poison, and probably the best combat choice for this level if the DM allows dinosaurs.

4th:
Fleshraker Dinosaur (MM3): An awesome choice - pounce, grapple, rend, and poison!

7th:
Snake, Huge Viper: A good grappler with constrict, but the poison DC is low.  A sea snake adds +2 to the poison DC and can swim as well.

13th:
Giant Banded Lizard (Sandstorm): a huge grappler with a decent poison (DC 21, 2d4/2d4 Strength). 

Familiars:
Tiny Viper: DC 10, 1d6/1d6 Con damage, and +3 to bluff checks.
Sea Snake (Tiny) Stormwrack: DC 12, 1d6/1d6 Con damage.  Strictly superior to a viper.

Improved familiars and similar:
Homunculus (7th): a scout with a decent poison, though I'd rather have the imp.  DC 14 - sleep for 1 minute, then DC 14 or sleep for 5d6 minutes.  It's a good option for artificers.
Imp (7th level): besides being a good utility familiar and scout, you can use its weak dex poison just by asking for it.  DC 14, 1d4/2d4 Dex damage.  Plus he's immune to poison, so he can shoot black lotus slathered darts for you later on. 
Pseudodragon (7th): immune to sleep and paralysis, but you need to be neutral good.  Also has a DC 14 sleeping poison you can ask for from it.  But it's something you can probably use as a good-aligned character.

Purchasable Creatures:
 
Wyvern (A&EG): at 3,000 GP for a young wyvern, it's a good deal.  Useful as a mount as well, obviously.

Spider Eater (MM): 2,000g for an egg, a flying mount with poison.

Giant Wasp (A&E, MM): 750g for a larvae, but wasps aren't that great.  Still, it's pretty cheap.

Monstrous Scorpion, Huge (A&E, MM): 1,000g for an egg.  Not bad at all!

Adamantine Spider (DoTU): you can create these constructs for 5,450g or buy them for 10,900g, and they can be upgraded as well.  Each one can carry a single dose of poison that it injects with its bite attack.  Good for an artificer.

Warbeast creatures (MMII): This extremely template can be applied to any animals or vermin, which conveniently gives a price for warbeast animals.  So find something with a poison you like and buy a warbeast version of it if you can.  In general animals purchased this way will be stronger AND cheaper than any other method, and therefore also much more likely to be disallowed.


10. Equipment and Magic Items:

Special materials & modifications:
Chaos Flask (Planar Handbook): A 100g flask containing raw chaos that you can shape into a temporary dose of poison with a DC 13 Wisdom check.  Very versatile, but requires some DM oversight if a dose of poison constitutes a single 'object', and also must be used within 1-2 minutes for most characters.  Shapesand from Sandstorm is another similar material that can be turned into poisons easily.
Spiderblood, Drow (A&E): a drink, not a poison.  Those used to the wine ignore its effects, but others take some con damage.  Good for the classic "I drank the wine, so you know it's safe" cliche (And remember: never go up against a Sicilian when death is on the line!)
Breathing Hood (DoTU): 70g for a hat that gives +8 to saves against inhaled poisons.  Buy some for your party members if you use inhaled poisons such as sleep-smoke frequently.
Mister (DoTU): 150g for a way to hit an opponent with an ingested, injury, or contact poison as a ranged touch attack from 5ft away.  Gives a DC 15 reflex check against ingested poisons and injury poisons only work on wounded opponents, but still a great item.
Hilt Hollow (Dungeonscape): good for carrying hidden poisons and for getting them out as a swift action.  At 200g, it's cheap too. 
Oil Chamber Dungeonscape: lets you spray oil, etc. from your weapon as a swift action. Poisons as well, but you're automatically exposed, so it's only worthwhile if you're immune to the poison.  Costs 1,000g, so it's this or a spyglass.
Weapon Capsule Retainer and Triple Weapon Capsule Retainer (C. Adventurer): For 100g or 450g, this allows you to store up to three injury poisons in a melee or thrown weapon.  As a swift action, you can apply 1, 2 or all 3 of the injury poisons held to the weapon.  While its probably unintentional that you can use this to stack 3 poisons at once, even without that ability this allows a poison user to quickly switch poisons on a melee weapon, or replace them in the middle of a fight, effectively granting the speedy poisoning ability of the Master of Poisons feat to anyone who has the normal Poison Use ability. 

Magic items:
Assassination (Cityscape Web Enhancement): A +1 enhancement that grants 1d6 sneak attack and increases the save DC of any poison it delivers by the weapon's enhancement bonus (so +4 to the DC if it's a +4 Assassination Sword, etc.).  Lastly, The wielder never risks poisoning herself when applying poison to an assassination weapon.  This is the biggest DC booster for poisons!
Venomous (MIC): a +1 weapon enhancement that gives a weapon a weak poison 3/day as a swift action.  Not worth getting in most cases.
Virulent (DoTU): A +1 weapon enhancement that reduces the duration for contact and injury poisons down to 5 rounds before the second save.  Excellent.
Toxic (DoTU): A +1 weapon enhancement that makes a poison last for 2 rounds per hit instead of a single round.  Excellent.

+1 Feycraft Assassination, Toxic, Virulent Dagger, Triple Weapon Capsule Retainer, Hilt Hollow, and a Tooth of Leraje: 33,803g, 650g, and 20,000g for a weapon that's +5 to hit and damage, +5 to poison save DC, allows you to use poisons without poisoning yourself, you can apply poison to the weapon 4/encounter as a swift action, the poisons last for 2 hits each, and the secondary save is in 5 rounds rather than 10 rounds. 

Other:
Collar of Venom (BoVD): granting all natural attacks a d10 poison effect seems like a good deal to me!  The only problem is the low DC and the high cost.  The Collar of Virulent Venom gets the DC to 20, but is ridiculously expensive.  Still, either collar would be an insane combination with Venomfire for a druid in wildshape.
Poison Fangs (Serpent Kingdoms): For 8,000 gold, give yourself poisonous fangs for free poison!  The DC scales with your level and Con modifier, which helps this scale much better than many abilities. 
Arrow of Biting (MIC): Ah, memories of 2nd edition!!  Anyhow, this has a decent poison, and is cheap enough for artificers to craft if they've focused on Craft Arms & Armor or have other cost reducers. 
Amber Amulet of Vermin (MIC): 700g to summon a huge scorpion 1/day.  I've gotten this item banned in arenas before.  Besides wiping the floor of anything you face at 2nd level, it also gives you a source for some DC 18, 1d6/1d6 Con damage poison.  Later errrata'd to a large scorpion.
Toxic Gloves (MIC): good as a cheap source of decent con-draining poison 3/day. 
Spider Rod (MIC): A melee touch attack with the poison spell all day long, plus a few uses of an entangling net effect.  Decent for the price.


11. Spells:

In general, any spell that reduces an oppponents' saves is good along with poisons.  Shaken, sickened, level drained, and cursed opponents all are more likely to succumb to poisons, for example. 

0 Level
Detect Poison: While its normally the bane of your existence, this spell can be very handy for you while searching for poisons or poisonous creatures in the wild.
Launch Object (SpC): This handy cantrip lets you throw inhaled and contact poisons up to ridiculous distances, from 110 to 300 feet away!

1st Level
Breath of the Jungle (SpC): Druid 1, affects a huge area for several minutes and increases the save DCs against poisons by 2 within the cloud.  No save or SR.
Charm Animal: convince an animal that it's a good idea to let you squeeze some venom out of its fangs.
Magecraft (EBCS): gives +5 competence on one craft check for a low-level sorc/wiz.
Summon Monster/Summon Nature's Ally I: all of the low-level versions of these spells can summon poisonous creatures for you to get venom from, probably in conjunction with Charm Animal and Speak with Animal.
Psionic Minor Creation: Notable for being 1st level.  Especially nice on a follower for a poison user who can't create poisons magically.
Chill Touch: use with Poison Spells to get five uses out of a single dose of poison, and to stack strength damage quickly.

2nd Level
Alter Self: I believe you get natural poisons when you cast alter self.  The same goes for Polymorph and Shapechange.  This could be useful for elans or dragonwrought kobolds.
Increase Virulence (PHB II): A 1-minute casting time and only lasts for minutes/level, but increases a poison's DC by 2.  Situationally good, but a great spell to prepare before an ambush. 
Unseen Crafter (RoE): Summons an unseen servant to continue your craft checks while you sleep or go out for drinks.  With a day/level duration, you can cast this the day before you go off on an adventure, and come back home to pick up your poisons a week later.

3rd:
Animate Dead: skeletons don't mind being doused in poison or exposing themselves to a poisoned sword.
Poison: The spell's DC scales very well with CL and goes perfectly with Poison Spell. 
Shrink Item: for when you've got barrels of black lotus extract lying around.
Toxic Tongue (CM): this assassin-only spell is a solid pick, giving a use for swift actions during combat and dealing con damage.
Venomfire (Serpent Kingdoms): If you're casting this spell often, you don't really even care if something makes the save against your poisons, because this spell puts poison damage to shame. 

4th:
Minor Creation: temporarily make some plant-based poisons with a skill check.  Lasts for hours/level, so it's feasible to cast this once per day at higher levels. 
Fabricate, Psionic: As Fabricate, but 1 level lower.
SNA IV: summon a huge viper for its poison, or a unicorn to get a free Neutralize Poison.
Giant Vermin: after the fight, milk your colossal pets for their high DC poisons.  Or cast it during downtime.

5th:
Animal Growth: like Giant Vermin, use it get poisons from larger-than-normal versions of animals you summon or keep around.
Fabricate: make lots of poisons with a skill check.  Requires the raw materials beforehand. 
Major Creation: Doubles the duration of plant-based poisons compared to minor creation, and allows stone or mineral based poisons as well.

6th:
Planar Binding: Bind a Djinni for permanent duration Major Creation with plant materials, or a fiendish wyvern for poisons.  Very flexible spell.

7th:
Shadow Conjuration, Greater: This can be used to mimic Minor/Major Creation - useful if you value versatility.

8th:
Polymorph any Object: Can possibly create poisons with a permanent duration, depending on your DM's interpretation of whether a poison qualifies as having "great intrinsic value."  Considering the high cost of poisons in D&D, I think they probably do qualify, sadly enough.
Planar Binding, Greater: Bind a Pit Fiend, and use its venom as the raw materials to make your own doses.  Plus, you get a pit fiend. (Thanks Eldariel!)
Befoul (FC I, Lords of Madness): Permanently turns a lake into poison.  Weak, ingested poison.

9th:
Gate: Same as Planar Binding.

[Libertad]

12. Poisons:

This lists some of the best poisons in the various 3.0 and 3.5 books out there.  Black Lotus Poison gets all the attention, but there is actually a wide variety of poisons that are good to use, even if you only use Minor Creation. 

My favorite poisons are:
Black lotus poison, drow poison, sleep-smoke, stun gas, roach paste, yew, belladonna, good-bye kiss, spotted toadstool venom, sassone leaf residue, sinmaker's surprise, darklight brew, (greater) sskalor venom, pit fiend venom, elemental rime, siren's breath, stingray venom, and crystal scorpion venom.  About half of these are craftable using Minor Creation, while many others are easy to find or very cheap to make, and others provide excellent status effects like stunning, exhaustion, and nauseate, while a few simply have high amounts of stat damage and high DCs. 

Poisons by lowest base cost
Terrific buys for their value.  These are listed at market value, not cost to create - so with the materials on hand, they would instead cost 1/6th the listed price here.
25g: Sleep-Smoke (Waterdeep, City of Splendors Pg. 152.  Unconsciousness/Unconsciousness!)
40g: Tiny Centipede poison (Core; 1 dex woo!)
40g: Stun Gas (A&EG 37, Stuns!)
50g: Roach paste (DoTU 94; Nauseates!)
50g: Darkeye (Sharn, City of Towers; Paralysis!)
75g: Drow poison (Core; Unconsciousness!)
75g: Snowflake Lichen PowderFrostburn (1 Dex/1 Str!)
90g: Oil of Taggit (Core; 0/Unconsciousness and ingested
100g: Taxine (Yew tree poison.  Ingested: 1d3 Con/2d6, each subsequent exposure increases DC by 2 and +1d2 Con damage)

Minor Creation and Major Creation: Plant and mineral based poisons
Craft DC 15/None: Belladonna (Monster Manual).  Ingested: DC 13, 1d6 Str damage/2d6 Str damage.  No craft check necessary for just the raw plant, which is poisonous.
Craft DC 15/None: Yew (Online).  Ingested: DC 13, 1d2 Con damage/2d6 Con damage.  No craft check necessary for just the raw bark or leaves, which is poisonous.
Craft DC 15/None: Striped Toadstool (DMG).  Ingested: DC 11, deals 1 Wis/2d6 Wis and 1d4 Int.  Presumably no craft check necessary for just the raw toadstool.
Craft DC 15?: Stun Gas (Underdark).  Inhaled: DC 12, Stun effect.
Craft DC 15/None: Volcanic Gas (Sandstorm).  Inhaled: DC 13, Unconsciousness/1d6 Con.  Major Creation should work with this.
Craft DC 15: Blue Whinnis (DMG).  Injury: DC 14, deals 1 Con/Unconsciousness
Craft DC 15: Bloodroot (DMG).  Injury: DC 12, deals 0/1d4 Con +1d3 Wis
Craft DC 15: Arsenic (DMG): DC 13 Ingested, 1 Con/1d8 Con.  The "King of Poisons" is quite tame in D&D, and can be crafted with Major Creation.
Craft DC 15: Sleeping Vine (A&E 37): DC 13, slowed/1d4 Dex
Craft DC 15: Id Moss (DMG): DC 14 Ingested, 1d4 Int/2d6 Int
Craft DC 15: Good-Bye Kiss (C. Scoundrel) Contact: Exhaustion/Exhaustion, Fatigued on a successful save)
Craft DC 15: Drow Poison (DMG) Injury DC 13, Unconsciousness/Unconsciousness. *Noted as being distilled from fungi and roots in C. Scoundrel
Craft DC 17: Psychotropic Rot (DoTU 94): Ingested: DC 15, deals 1d4 Wis/3d8 Hp.
Craft DC 20: Vapid Leaf Extract (A&E 37): DC 16, Dazed/2d6 Int.
Craft DC 20?: Spotted Toadstool Venom (Player's Guide to Eberron).  Injury: DC 16, 1d6 Str/1d6 Con.
Craft DC 20: Malyss Root paste (DMG).  Injury DC 16, deals 1 Dex/2d4 Dex damage.
Craft DC 20: Sassone leaf residue (DMG): Contact DC 16, deals 2d12 damage/1d6 Con.
Craft DC 21: Cave Terror (Underdark).  DC 20, Confusion effect.
Craft DC 25: Terinav Root (DMG).  Contact DC 20, deals 1d6/2d6 Dex.
Craft DC 25?: Sinmaker's Surprise (Manual of the Planes).  Injury DC 24, Ingested DC 18.  Deals 1d6 Con/2d6 Con, and 1d6 Acid for 3 rounds.
Craft DC 28: Darklight Brew (DoTU 94): Injury DC 23, Deals an initial 2d6 Con and 1d6 Strength damage, and blindness as a secondary effect!  Can be crafted with Major Creation.
Craft DC 35: Black Lotus Extract (DMG).  DC 20, deals 3d6/3d6 Con.
Craft DC 35?: Greensickness (Dungeonscape, MMIII).  DC 33, deals 2d6 Str + 1d4 Con/2d6 Str + 1d4 Con.  *Confirmed that this is plant-based - it's from the Plague Brush in MMIII, an extraplanar house-sized tumbleweed of death.  Words fail me.  Craft DC given is an estimate by PlzBreakMyCampaign, my own inclination would be to make it DC 40 or 45.

For GOOD-aligned adventurers and crowd control: Sleep, paralysis, unconsciousness, and other non-lethal poisons listed by save DC
DC 34: Svakalor Venom, Greater (Paralysis/1d6 Con) (Dungeonscape)
DC 24: Svakalor Venom (Paralysis/4d6 Con) (Dungeonscape)
DC 22: Eyeblast (Blindness) (C. Adv?)
DC 20: Sssartisss (Paralysis 2d6 mins/Unconscious) (Serpent Kingdoms)
DC 18: Scorcher Fumes (Lose the Scent ability) (A&EG 37)
DC 17: Lizardfolk Sleep Poison (Contact, Unconsciousness 1d3 rounds/Unconsciousness 1d3 hours) (Serpent Kingdoms)
DC 15: Oil of Taggit (0/Unconscious) (Core)
DC 15: Good-bye Kiss (Exhaustion/Exhaustion, Fatigued on a successful save) (C. Scoundrel)
DC 15: Sleep-Smoke (DC 15 Unconscious/Unconscious 1d3 mins) (Waterdeep, City of Splendors 152)
DC 15: Coldrith Toxin (Paralysis/2d4 Con) (A&EG 37)
DC 15: Retch (Nausea) (A&EG 37)
DC 15:  Wild Dwarf Knockout Poison (Slows for 5 rounds, then unconsciousness) (PGtF)
DC 14: Homonculus venom (Sleep)
DC 14: Pseudodragon venom (Sleep)
DC 13: Carrion Crawler Brain Juice (Paralysis) (A&EG 37)
DC 13: Sleeping Weed (Slowed/1d4 Dex) (A&EG 37)
DC 13: Drow Poison (Unconsciousness/Unconsciousness) (Core)
DC 12: Roach paste (Nausea for 1 round/Filth Fever) (DoTU 94)
DC 12: Brain Dust (Confusion) (A&EG 37)
DC 12: Darkeye (Paralysis 1 min, ingested) (Sharn, City of Towers)
DC 11: Lockjaw (Can't speak) (A&EG 37)

Real World Poisons in D&D:
Craft DC 15: Arsenic (DMG): DC 13 Ingested, 1 Con/1d8 Con.  The "King of Poisons" is quite tame in D&D, and can be crafted with Major Creation.
Craft DC 15/None: Belladonna (Monster Manual).  Ingested: DC 13, 1d6 Str damage/2d6 Str damage.  No craft check necessary for just the raw plant, which is poisonous.
Craft DC 15/None: Yew (Online).  Ingested: DC 13, 1d2 Con damage/2d6 Con damage.  No craft check necessary for just the raw bark or leaves, which is poisonous.
Craft DC 15/None: Striped Toadstool (DMG).  Ingested: DC 11, deals 1 Wis/2d6 Wis and 1d4 Int.  Presumably no craft check necessary for just the raw toadstool.  Not actually a real fungus, but the stats can stand for any number of actual poisonous mushrooms like amanitas (red with white dots), false morels, jack-o'-lanterns, and green-spored lepiotas.
Craft DC 15: Black Adder Venom (DMG).  Injury: DC 11, deals 1d6 Con/1d6 Con.
Craft DC 15: Small Centipede Poison (DMG).  Injury: DC 11, deals 1d2 Dex/1d2 Dex.
Craft DC 15: Tiny Spider (MM).  Injury: DC 10, deals 1d2 Str/1d2 Str.
Craft DC 15: Tiny Scorpion (MM).  Injury: DC 11, deals 1 Con/1 Con.

Poisons by highest damage on initial hit (non-epic)

Strength
3d6 Str: Dragon Bile
3d6 Str: Ulathlasss Smoke (Serpent Kingdoms, Inhaled)
2d8 Str: Colossal Spider/Scorpion venom (pre-errata)
2d6 Str + 1d4 Con: Greensickness (DS)

Dexterity
2d6 Dex: Colossal Centipede poison  (pre-errata)
2d6 Dex: Redek Vine Extract (A&EG 37)
1d8 Dex: Stonefish Venom Stormwrack
1d6 Dex: Giant Wasp Poison

Constitution
3d6 Con: Black Lotus Extract
2d6 Con+1d6 Str: Darklight brew (DoTU 94)
2d6 Con+1d4 Dex : Megapede venom
2d6 Con: Wyvern venom

Intelligence
1d6 Int: Illithid Mindscorch (DoTU 94, inhaled)
1d4 Int: Rishon Vapor (A&EG 37)
1d4 Int: Jalass Smoke (Serpent Kingdoms, Inhaled)

Wisdom
1d6 Wis: Doubt Bomb (Fiend Folio)
1d4 Wis: Insanity Mist (A&EG 37)
1d4 Wis: Psychotropic Rot (DoTU 94, ingested)
1d4 Wis: Battass Smoke (Serpent Kingdoms, Inhaled)

Charisma
1d6 Cha+1d2 Con: Slowswarming (DoTU 94, ingested)
1d6 Cha: Raeliss Smoke (A&EG 37)
1d6 Cha: Burning Angel Wing Fumes (BoVD, of course)

Straight damage/other damage:
2d12 HP Dmg: Sassone Leaf Extract (core)
4d4 HP Dmg: Ts'ous (Serpent Kingdoms, injury)
1d6 HP Dmg: Hooloond Smoke (Serpent Kingdoms, inhaled)
1d6 HP: Slow Death (C. Scoundrel, 1d6/rd for 5 rounds)
2d4 Acid Dmg: Laerisss Smoke (Serpent Kingdoms)

Poisons by highest DC (Most can be found on Pg. 129 of Dungeonscape)
DC 54: colossal scorpion venom (3.0 BoVD, this was later errata'd in Dungeonscape to DC 33 and a lower initial/secondary damage)
... after this are about 10 more poisons from 3.0 gargantuan and colossal vermin that range in the 40's and 30's.  I'm going to avoid listing all of those iterations, as they are errata'd to much lower DCs in Dungeonscape.  44 is basically the highest save DC now.
DC 44: Megapede Venom (DS)
DC 34: Svakalor Venom, Greater (Dungeonscape)
DC 33: Colossal Scorpion Venom)
DC 33: Greensickness (Dungeonscape)
DC 28: Colossal Spider Venom
DC 27: Pit Fiend venom (Dungeonscape)
DC 27: Colossal Purple Worm Venom (DS)
DC 26: Dragon Bile (DMG) 
DC 25: Purple Worm Poison (DMG).  Note that the DC was increased in C. Adv.

Unique & Useful Poisons

Arms & Equipment Guide:
These poisons are listed on pages 37 and 38. There are 20-30 poisons in A&EG, but most of them are quite mundane.
1. Choldrith Toxin: the primary effect is paralysis, which is useful for races immune to paralysis, such as dragonwrought kobolds. 
2. Fang Dragon Venom: possible to acquire through Alter Self as a dragonwrought kobold.
3. Lockjaw: ingested and a low DC, but prevents all speech & somatic components.  As-is, it completely shuts down spellcasters, but I think it's clear that the designers meant that it would prevent all VERBAL components.

Book of Exalted Deeds: this book has ravages, which are good-aligned poisons.  I think the very idea is ridiculous, but who asked me?
1. Golden ice: only worth mentioning for the feat "Touch of Golden Ice"
2. Unicorn blood: You can summon a unicorn with Summon Nature's Ally IV and politely ask it for its blood after its done healing your party.

Book of Vile Darkness
1. Devilseye and Basilisk Breath both affect outsiders that are generally immune to poisons, so they might be worth crafting in some cases.

Complete Scoundrel:
1. Blasphemix (Injury): it's got a DC of 22 and is only 750gp, but forces divine spellcasters to make a stiff CL check for 10 rounds! (DC 15+spell level)  Requires Knowledge (Religion) to make.
2. Elemental Rime (Injury): At 200g, this is cheap to make, and though the save DC is low at 16, forcing a creature to gain Fire Vulnerability can set up some awesome combos with a blaster mage.  A duskblade, for example, can hit his opponent with Elemental Rime poison, and then swift action cast a Scorching Ray at the opponent.  Also requires Knowledge (the Planes) to make.
3. Goodbye Kiss (Ingested/Injury): The initial effect is fatigued, and the secondary Exhausted is a great effect!  Since it's both injury and ingested, it has decent applications in a fight and in roleplay situations.
4. Siren's Breath (Inhaled): gives -5 penalty to saves against enchantment spells.  A little pricey at 300g though.
5. Salvo (Injury): Notable for the incredibly low Craft DC of 12.  The effect isn't particularly good, but this could be a potent money-making poison to create in drow cities or large metropolises.  Thanks telehax!

Drow of the Underdark:
Page 94 lists various poisons and magical poisons. Definitely some of the most creative and varied in any sourcebook.
1. Darklight Brew (Injury): A DC 23 poison that deals an initial 2d6 Con and 1d6 Strength damage, and blindness as a secondary effect!  It's ridiculously expensive, but is made from darklight ore, which means that it can be crafted with Major Creation.  A great high level poison.
2. Roach Paste (Injury): Only DC 12, but only 50g to make and causes nausea for 1 round.  Great at low levels, and the components are from giant roaches, which is absolutely disgusting but easy to find.
3. Underdark Blight (Contact): Another poison made from ore, this one lowers SR by 1.

Magic-infused poisons from DoTU: These require a spell cast when making them, but are much stronger than normal poisons. 
1. The Calling (ingested): you summon a swarm of spiders from inside somebody's belly if they ingest the poison, which requires a DC 20 profession (cook) check to detect.  Gross!
2. Creeping Nullscourge (Injury): A DC 20 poison that lowers SR by FIVE on initial and final contact!  Requires Assay Spell Resistance to create, but talk about a great effect!
3. Slow Taint (Contact): Reduces a target's speed by 10ft/10ft for 1 hour.

Dungeonscape:
Greater poisons: these are poisons from advanced creatures such as gargantuan scorpions.  No craft DC is listed, but it can be extrapolated from the save DC and cost.
1. Greensickness is a DC 33 inhaled poison, which is the highest you'll find for that type of poison, AND it's plant-based!
2. Pit Fiend venom is DC 27 injury, but the secondary effect is death!  Now all you have to do is find a pit fiend...

Libris Mortis: positoxins are poisons that affect undead, only they are made with Alchemy.  They are expensive to make, but hey, it's something.  They need the help of a positive-energy channeling character though.
1. Gravedust and Boneshard Paste should both be manufacturable with Major Creation, or possibly by cutting up the skeletons you just defeated.

Races of Faerun: only 2 poisons in this book, but both are good.
1. Drow Poison.  At only 75 gp, this DC 13 or unconsciousness poison costs 12.5 gp/hit if you have the materials at hand, and unconsciousness is a damned good condition effect.  Best to hit an opponent with a con-reducing poison first to lower their saves.  Good as a low-level poison.
2. Wild Dwarf Knockout Poison: Slows opponents for 5 rounds and then unconsciousness.  A little pricey at 150 gold, but nice for wild dwarves, who are immune to the effects.
3. Tanglepatch: an alchemical substance - creates an entangle spell for only twice the cost of a tanglefoot bag.  Pretty sweet.

Stormwrack: See page 13
1. Sea Snake venom: Sea snakes can be taken as a familiar at 1st level, so for a low-level wizard who wants a source of poison, this is pretty solid, as their venom has a DC of 2 higher than that of a viper of comparative size. 
2. Sekulah's Judgment: Ingested, but a high DC and deals 1d6 Con + nauseated for 2d6 rounds, with a secondary effect of 3d6 Con damage.  Best of all, even on a successful save the target is nauseated for 1d6 rounds!  One of the few ingested poisons worth considering in combat.
3. Fire coral extract: in case you need another source of a cheap, low-level nauseating poison!
4. Stingray venom: just to note that a druid can probably harvest venom from a stingray animal companion that is quite effective.


Sandstorm: See page 24.
1. Crystal scorpion venom: made from normal monstrous scorpions, this is an excellent poison.  Contact DC 19, -/Helpless 1d4 hours, entangled 1d4 days.  DC 25 Alchemy or DC 21 Craft (Poison) to create, 1,500 gp base cost.  Terrific for those who can reduce or ignore the cost with Vermin Trainer. 
2. Dunewinder venom: A Contact 1d8 Con/1d8 Con poison that's expensive and comes from a rare monster.  Bah.
3.Volcanic Gas (Sandstorm).  Inhaled: DC 13, Unconsciousness/1d6 Con.   Craft DC 15/None: Major Creation might be able to conjure this.
4. Giant Banded Lizards: available as an animal companion to druids of 10th or higher, and have improved grab, high damage and AC, and an excellent bite poison: DC 21 2d4 Str/2d4 Str, increases with Con.
5. The Ironthorn: available as a druid wildshape form at 9th with Enhance Wildshape or 15th otherwise, this is an amazing defensive wildshape form.  It has AC 24, and with Enhance Wildshape this form can get 60ft Blindsense and DR 5/bludgeoning.  Comes with 15ft reach, Improved Grab, and Impale (like a rake).  Poison: Injury DC 23, initial paralysis/secondary 2d4 Con, poison is con-based (so if your Con is higher than 25 the DC will scale up).  Great both in downtime and as an actual combat form.  Protip: get a magical fly speed as well (Overland FLight!) to counteract the slow land speed.

Online:
Taxine (Yew tree poison): This is very handy, since it's easy to acquire and likely very cheap.  No listed craft DC - it appears this is the base poison simply for eating the bark or leaves of the yew tree.
Taxine (yew tree poison): Ingested DC 13; initial damage 1d2 Con; secondary damage 2d6 Con; additive effects (taxine builds up in the system; each subsequent dose of taxine adds +2 to the Fort save DC to resist the poison's effect and adds +1d2 Con damage to the secondary damage); price 100 gp.  Thanks Garryl! 

Kiss of the Grave: a fairly weak initial poison (1d4 Con damage), but its secondary damage makes immortal creatures mortal. It also makes them unable to be raised or resurrected, and takes a Wish or Miracle to remove the effect. Contact poison, DC 20.  Thanks Garryl! 

The Epic Level Handbook Web Enhancement
These poisons all require the Epic Poison Crafter Feat (so level 27+).  However, they are immune to all magical effects to prevent or avoid poisons.  The Godsblood poison seems to be the only one with a fortitude save that creatures at this level might actually fail.

Courtesy of Ed Zero

(click to show/hide)

Poison: Chaos Ichor
Type: Contact DC 22
Initial: 1d4 Str
Secondary: 2d6 Str
Price: 330,000gp
DC to Create: 53

Poison: Lyzeum
Type: Injury DC 25
Initial: 1d6 Dex
Secondary: 3d6 Dex
Price: 390,000gp
DC to Create: 59

Poison: Illis thyr
Type:Injury DC 28
Initial: 2d4 Con
Secondary: 4d4 Con
Price: 450,000gp
DC to Create: 65

Poison: Milk of Atropos
Type: Injury DC 32
Initial: 2d8 Str
Secondary: 4d8 Str
Price: 590,000gp
DC to Create:  79

Poison: Godsblood
Type: Injury DC 40
Initial: 1d6 Int
Secondary: 3d6 Int
Price: 820,000gp
DC to Create:  102

Serpent Kingdoms:
This has a large selection of poisons. 

The various smoke poisons (some of which are listed above in the lists) have a unique mechanic - unlike other inhaled poisons, these fill a 50-ft square for 4 hours or 5 rounds with the poison, which also acts as a nonmagical fog cloud spell. 

Want to fill a 50ft square with 3d6 Strength damage that isn't magical in any way?  This is where you want to go then.  They have some unique effects as well - Duthlah'hass has a 2d6 minute Feeblemind effect, easily the coolest one.  The smokes also act as BUFFS to Scaled Ones, a large category that includes kobolds and anything reptile-like that isn't a dragon (so dinosaurs, etc).  So any kobold can just light these suckers up and enjoy free buffs while his party and enemies all run around dying.  The following poisons from the list are plant or mineral based for Creation spells: Battasss (Wis/Sleep), Duthlah'hass (Feeblemind), Ektharisss (1d6/1d4 Str).

Dragon Magazine #301, Pg. 58
This issue has an article on various alchemical items in the "Poisons and Malefics" section. Thanks Maat_Mons!

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Other:
Aboleth Mucus (Savage Species): This is an alchemical item rather than a poison, but works as a contact or inhaled poison.  Victims who fail a DC 19 Fort save lose the ability to breath air for 3 hours, which means most will suffocate in 1-4 minutes.  A save or die for only 20g, and quite likely to be insta-banned.  Cost: 20 gp; Weight: 1 lb.
Mordrei'in: Created by the Aereni elves for use in religious rites, mordrei’in (or “leaves of death”) is made of the crushed leaves of the rare mordril tree, combined with other sacred herbs and powders. When eaten raw, the leaves are a deadly poison (Fortitude DC 14, 1d6 Con/1d6 Con).  Mordrei’in, however, enhances the imbiber’s ability to focus and is substantially less toxic (Fortitude DC 10, 1 Con/1 Con). Anyone who consumes mordrei’in (whether or not the save succeeds) gains a +2 alchemical bonus on Concentration and Spot checks for 10 minutes.
Price 25 gp (available only on Aerenal). (Faiths of Eberron - thanks Ed-Zero!)
Darkeye 50gp, Alchemy DC: 25.  A toxic beverage: DC 12 ingested, paralysis/secondary damage 1 Con. However, if the victim fails his saving throw against the secondary damage, the paralysis continues and he must make another save after a minute has passed. This continues until the victim makes a successful saving throw.
During the period of paralysis, the victim is poised on the brink of life and death. Some victims see visions of their past, while others hear the voices of departed friends and family. The experience sensitizes the victim to the emanations of the beyond. For an hour after consuming darkeye, the victim gains +1 effective caster level when casting any sort of necromantic spell; this is increased to +5 when casting speak with dead.  Darkeye is terribly bitter, and a full dose (2 ounces) is required to have any effect.(Sharn, City of Towers)
Blister Oil (Races of Stone): an alchemical substance, but dirt cheap (5gp for 1-8 uses), and works as an injury poison to deal some damage and penalize Dex checks and reflex saves.  Great for low-level alchemists, and doesn't carry the drawback of poisoning yourself if you mess up.
Scentbreaker (Tome & Blood): a cheap thrown alchemical substance that removes the scent quality for 1 hour, DC 15 or DC 18 on a direct hit.  Thanks snakeman830!
Stun Gas (Underdark): At 40gp (6.6gp self-crafted), this is one of the cheapest poisons around!  DC 12 inhaled, and stuns for 1/1d4 rounds.  A dose can be stored in darts and presumably arrowheads.  Great for low levels.
Sleep-Smoke (Waterdeep: City of Splendors 152): At 25g (4.16g self-crafted), this is a DC 15 inhaled poison that lasts 2 rounds - first in a 10ft globe, then in a 20ft globe!  Both the primary and secondary effects are unconsciousness (1 min/1d3 mins).  DC 15 to create.
Doubt Bomb (Fiend Folio, 3.0) - 500gp for a grenade that shatters on impact, creating a cloud of poisonous gas in a 10-foot spread (initial and secondary damage 1d6 Wisdom, Fort DC 15 negates). Ethergaunts are immune to the effects of doubt bombs.
Sinmaker's Surprise (Manual of the Planes, 3.0) Fortitude Save: DC 24 (injury) or DC 18 (ingested), deals 2d6 Con on initial hit, along with 1d6 acid damage for 3 rounds, and then after a minute another 2d6 Con damage.  Made from leaves, so its usable with Minor Creation.  Price: 4,400gp.  Craft DC: ??
Venomous Fire (Fiend Folio): This is alchemist's fire and poison (DC 17/17 1d6 Con) mixed together - both rounds of fire expose the victim to a dose of poison, and a splash deals 1 point of fire damage, while a target hit by the splash has +4 circumstance bonus on the Fortitude save against the poison.  Cost: 220 gp; Weight: 1 lb.

Drugs

Drugs are similar to poisons, except in 3 ways:
1. They require Craft (Alchemy) to create, but function like poisons, including initial and secondary effects over the period of a minute.
2. They have addictions that come with them, along with a variety of beneficial and damaging effects.  For example, a drug might give a +2 bonus to strength for an hour, but deal 4 wisdom damage.
3. If you're hit by the same drug twice within a specific period, you suffer an overdose effect, often quite debilitating. 

Specific drugs: (ignoring useless ones)

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Book of Vile Darkness:
Agony (liquid pain): Notable because it's also used as a material component or as a substitute for experience in spells.
Baccaran: Another ingested one, this time with a nice side benefit for clerics who take it.
Devilweed: It's a cigarette (or a joint).  You can create it with Minor Creation, but it has no particular combat use for you, though it is dirt cheap and gives a nice little strength buff, so I'd actually smoke them as a melee type and pretend to be Dirty Harry or something. 
Luhix: Jackpot!  This is an  injury drug (Fort DC 25 or -1 to all ability scores), and the overdose effect is death (Fort DC 25).  It's expensive, but also made from plant material, so you can make it with Minor Creation.  Use it as an expensive injury poison.
Terran Brandy: It's green alcohol that gives a solid CL buff, but it's expensive and the OD effect is weak.  Still, cute idea.

Lords of Darkness:
Kammarth: A contact poison, but only DC 10.  Still, 2 hits leaves an opponent paralyzed, and it's moderately cheap too.
Oruighen: Basically Mace.  Make a melee touch attack to throw tiny pellets at your opponent to blind him and give -2 to saves, skill checks, and attacks.  Only 20g! 
Rhul ("Battlewine"): It turns you into a barbarian!  Very useful, actually, even if the OD effect is pretty weak.
Sezarad Root: Ingested and a weak DC.  Weird, but kinda useful to munch on.

Conclusions: Luhix is the only one worthwhile as a standard poison, though some of the others have other uses.

[Libertad]

COMPLETE BUILDS from various Iron Chef challenges:

Hugo Clopin, by Akal-Saris.
NE Strongheart Halfling Beguiler 5/Mindbender 1/Psionic Assassin 1/Psibond Agent 10/Magical Trickster 3.  See post #174 for the build - it uses poisons while being almost undetectable and mentally controlling minions and opponents at-will from 100ft away.

Danny and Rusty, by FishAreWet.  Changeling Rogue 1/ Psion (Shaper) 7/ Black Dog 2/ Psibond 8 / Ghost 2.  See post #187 for build.  It uses true mind switch and psionics to make poisons and the minions to deliver them.

Jorath, the Hand of Annihilation, by Akal-Saris. 
LE Human Paladin of Tyranny 4/Hexblade 4/Blackguard 7/Entropomancer 5.  See Post #116.  A tank build.  Debuffs saving throws by about -8 to -14 so that opponents are almost guaranteed to fail their saving throws against poisons.

Nicolo Egidi, by Amphetyron.  LE Halfling Rogue 1/Hexblade 4/Black Dog 5/Green Star Adept 10.  See Post #155.  A jack-of-all-trades build.  Was empower poisons, dhurinda's touch, and poison spell, he can apply poisons in several different ways (including a slam attack), and he has a wide array of resistances and armor from green star adept. 

Jungle Halfling Factotum 12 by JaronK

With Darkstalker, Poison Expert, Font of Inspiration X2, Poison Master, Sickening Strike, Terrifying Strike, using a Feycraft +1 Splitting Compound Longbow of Assassination.  Cast Greater Magic Weapon on your bow and go to town.  Use Inspiration Points to generate the necessary sneak attack, and Minor Creation for plenty of Black Lotus Poison.  It's DC 25, does 3d6+3 Con damage, and when you use your ambush feats the enemy is at -4 to saves, plus two attacks per turn force saves... so it's effectively DC 29 fort save on most attacks (and after one failure, the enemy won't stand a chance of succeeding).  And Splitting is of course an awesome enchantment for this as it effectively doubles your poison shots (plus you can poison your arrows in advance).  It might be advisable to take two levels of Swordsage for Assassin's Stance and other manuevers.

Saintx's Master of Shrouds
Human Cleric 1/Human paragon 2/Master of Shrouds 10
Notes: Uses the shadows that you can summon for shadow essence (from the DMG), which deals permanent str damage.  (Editor's note: Start with human paragon levels for the skills!)  Overall looks like a simple and very fun build to me.  I've played with a variant of this: Human Conjurer 1/Cloistered Cleric 2/Master of Shrouds 2.  Add in the Lolth's Caress feat to burn Turn Undead attempts to force immediate secondary effect saves for 2d6 more Str damage from Shadow Oil!

Saintx's Stormlord
Human Ranger 11/Stormlord 9
Notes: takes a lot of feats to qualify.  I also spent a lot of feats on twf and throwing.  Uses javelins.  Get a big snake animal companion to milk. Apply to all javelins which also count at +3 lightning burst thundering weapons for 2gp each.

The Simple Druid
Human Druid 19/Contemplative 1
Role: Unspecified, probably healer/tank
Use of poisons: at 1st level takes Master of Poisons, allowing him to use poisons from an animal companion or found using survival.  Starting at 11th, he has the Artifice domain, allowing him to create poisons magically, and he is immune to poisons starting at 9th level.  All feats are open (except Natural Spell and Skill Focus...).

The "I can apply 10 poisons in a round, what can you do?" Duskblade.
Human Duskblade 20
Role: party tank/damage

Feats:
1st hmn: Master of Poisons
1st char: Poison Spell
3rd char: Obtain Familiar
6th char: Improved Familiar
9th char: Smiting Spell
12th char: Arcane Strike
15th char: Arcane Disciple (Artifice domain)
18th char: Open

Use of poisons: at early levels can apply one dose of poison over multiple rounds with chill touch.  Then at 3rd can use his familiar's poisons as raw materials, and hit an opponent with 2 doses of poison in 1 round using Channel Spell with a poisoned touch spell and with a poisoned sword.  At 6th he can have a combat familiar or one with a stronger poison, who can also deliver a poisonous touch spell for him. 

At 9th he gains smiting spell, allowing him to release an extra touch spell in a fight (also carrying poison), and at 13th every opponent hit with the poisoned touch spell from channel spell in a full attack action is poisoned.  Later he rounds out the abilities with some common gish picks.  With channel spell, smiting spell, a spell storing weapon, a poisoned blade, and quick cast, he can hit 1 opponent with 5 poisons (and 4 touch spells) in a single round, and then apply 1 touch spell and poison to anyone else hit in that round.  Talk about going nova!

The Bag o' Potions Rogue
Human Rogue 1/Diviner 5/Unseen Seer 9/Alchemist Savant 5
Role: Skills/trap-finder

Feats:
1st hmn: Able Learner
1st char: Master of Poisons
2nd diviner bonus: Quick Draw (UA Fighter feats ACF)
3rd char: Two-weapon Fighting
6th char: Favored in House (Cannith)
6th diviner bonus: Rapid Shot (ACF)
9th char: Poison Spell
12th char: Brew Potion
15th char: Craven
18th char: Improved Two-Weapon Fighting
BAB +9, CL 19, SA +4d6+20.
Use of poisons: actually uses alchemy instead of poisons.  He can use his familiar's poisons as raw materials starting at 2nd level, and later can fabricate poisons himself.  Basically, his schtick is throwing vials of poisons and alchemical substances with ranged touch attacks along with sneak attacks.  At 20th level with a BAB of +9, he can throw 5 spellvials a round, each one containing a 3rd level spell laced with poison from poison spell as well as a poison or alchemical substance mixed with it, as well as dealing 4d6+20 sneak attack on each hit (10d6 with hunter's eye or whatever that ranger spell is).   Plus, he casts as a 19th level wizard, you know - just for kicks.

The Summoner
Human Conjurer 3/Master Conjurer 2/Malconvoker 7/Master Conjurer +8
Role: Battlefield control

Feats:
1st hmn: Spell Focus (Conjuration)
1st char: Master of Poisons
1st conjurer bonus: Augment Summoning (UA ACF)
3rd char: Obtain Familiar (Sea Snake)
4th bonus: Skill Focus (Spellcraft)
6th char: Open
7th bonus: Skill Focus (Bluff)
9th char: Open
12th char: Open
15th char: Open
18th char: Open

Use of poisons: has a sea snake familiar, giving +3 to Bluff checks for Malconvoker, and providing a source of poison for the conjurer and his party early on.  He can handle the snake's venom without trouble, giving him a little extra boost in combat when he runs out of Grease spells early on.  Starting at 3rd level, the character can summon tanar'ri, which are immune to poisons, and give them poisoned weapons.  At 7th, he can start creating much more potent poisons for free with minor creation.  In short, with a minimum of investment (ranks in Craft, a feat, and possibly a familiar), the character makes his PrC  much more threatening.

Divine Summoner
Half-Drow Cleric 5/Malconvoker 7/Contemplative 8
Role: Battlefield control, healing

Feats:
1st char: Master of Poisons
3rd char: Spell Focus (Conjuration)
6th char: Augment Summoning
9th char: Lolth's Caress
12th char: Skill Focus (Knowledge: Religion)
15th char: Open
18th char: Open

Notes: Lolth's Caress is the highlight over an arcane build here - the cleric can force a secondary save as a standard action using a turn undead attempt.  This makes poisons such as Nitharit (0 initial/3d6 secondary) and Shadow Essence (1 str initial/2d6 str secondary) much more useful.

The Bad Toucher
Human Necromancer 3/Master Specialist 10/Red Wizard 5/Archmage 2
Role: Damage Dealer
Feats:
1st hmn: Tattoo Focus
1st char: Master of Poisons
1st bonus: Scribe Scroll
3rd char: Spell Focus (Necromancy)
4th bonus: Skill Focus (Spellcraft)
6th char: Poison Spell
6th bonus: GSF: Necromancy
9th char: Quicken Spell
12th char: Spell Focus (Conjuration)
15th char: Open
18th char: Open
18th bonus: Open
Use of poisons: uses Poison Spell infused touch spells from 60ft away, combining with circle magic to make the save DC for Poison impossibly high, as well as all the standard high level wizard tricks.  And you can coat your summoned undead in poisons too.  Would make a decent BBEG actually.

The Master Trap-Finder
Strongheart Halfling Wilderness Rogue 5 (UA variant)/Trapsmith 5/Scorpion Heritor 10
Role: Skills Master, especially trap-finder (8 skills/level from rogue and scorpion heritor, 6/level from trapsmith), with a ton of bonuses and spells to trap-finding and disarming.

Feats:
Just 1 required feat and Master of Poisons really.

Poison usage: can Fabricate poisons starting at 10th level.  Also becomes immune to scorpion venom and has some poison-related abilities at 5th and 9th level of scorpion heritor.  Sneak attack: +8d6.

The 1-Hit Kill
Human Rogue 5/Assassin 9/Dread Fang of Lolth 6
Role: Damage and skills
Feats:
1st hmn: Master of Poisons
1st char: Poison Expert (Injury)
3rd char: Venomous Strike
6th char: Poison Master (Injury)
9th char: Craven
12th char: Sickening Strike
15th char: Terrifying Strike
18th char: Open
Use of poisons:
Gains: +8d6+20 sneak attack and 3d6 sudden strike, +12 (+16) to poison DCs (+2 Dread Fang, +2 Poison Expert, +2 Venomous Strike, +2 Increase Virulence, -4 to saves from sickening and terrifying strike).

The character ambushes foes, reducing their saves by 4.  Then the poison (let's say it's Black Lotus) deals its Con damage, and then after that the death attack goes off, with -4+Con damage to saves from sickened/terrified and whatever con damage the opponent took.  And then damage, of course.

The Sword & Crossbow
This is a character I designed for the GITP forums to effectively fight with a sword in one hand and a crossbow in the other, but it makes pretty effective use of poisons.

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Kalimor Srune'lett, NE Half-Drow Fighter 1/Rogue 3/Swashbuckler 14/Swordsage 2
Actual levels: Rogue 1/Swashbuckler 1/Fighter 1/Rogue +1/SB +1/Rogue 1/SW +14
ACFs: Drow swashbuckler 7, Drow Rogue 1, Drow fighter 1 (All from Drow of the Underdark), Spell Sense (C. Mage Rogue 3)
Note: suffers from multi-class penalties - sorry, there's no avoiding this if you actually use those in your game.

Total BAB: +18, total sneak attack: 9-11d6+20 per hit, total HD: 15d10+3d6+2d8

Stats: 32 PB
Str: 12 
Dex: 18   
Con: 14 
Int: 14 
Wis: 8 
Cha: 8

Feats:
1st: Versatile Combatant (DoTU)
1st flaw: Point Blank Shot
1st flaw: Precise Shot
2nd bonus SB: Weapon Finesse
3rd fighter: Crossbow Sniper (PHB II)
3rd: Hand Crossbow Focus (DoTU)
6th: Daring Outlaw (C. Scoundrel)
9th: Craven (Champions of Ruin)
12th: Improved Critical (Rapier)
15th: Staggering Strike (DoTU)
18th: Improved Critical (Hand Crossbow)

Skills: 8+2 = 10 skills from the rogue list.  Probably Hide, Move Silently, Tumble, UMD, Listen, Spot, Search, Craft (Poison), Balance, Sleight of Hand.

Starting equipment (estimates): Composite Shortbow (35g), Studded Leather (30g), Rapier (20g), self-crafted drow poison x3 (75g)

How it all comes together:

1st level: You have Poison Use from your Drow rogue substitution, plus the feats to use a ranged weapon efficiently - so you basically just snipe with a short bow and pretend you don't have versatile combatant or a hand crossbow yet.  You also have 3 poisoned arrows which can potentially end an encounter by putting an opponent to sleep.

2nd level: Now you have weapon finesse and +1 BAB, so you can use a rapier without missing consistently.  So you become the party tank!  You can also afford a masterwork chain shirt, masterwork tools (mostly for crafting poisons and searching for traps, I'd assume), and lots more poisons.

3rd level: Now suddenly you have Dex to damage against flat-footed opponents (Drow fighter), as well as 1/2 Dex to damage with crossbows (Crossbow sniper), plus weapon focus and rapid reload with a hand crossbow. 

So at this point the tactic of charging in with a crossbow and rapier actually becomes viable - assuming no magical bonuses and a pair of masterwork weapons, you should be attacking at +5 for 1d6+2 and 1d6 SA (1d6+4 against flat-footed) with the rapier, and +6 for 1d4+2 and 1d6 SA (1d6+4 against flat-footed foes) with the crossbow.  In addition to whatever poisons you've applied to your bolts and rapier - I like Roach Paste and Drow Poison on most things.

For equipment, a pair of MW weapons is good, as is picking up a str-based composite longbow and some more varied and higher DC poisons.

4th-5th level: Nothing special here, Dex gets bumped.  For items, I'd get the Gloves of Dexterity ASAP, and some weapon crystals for quickdraw on your weapons is very helpful (MIC).

6th level: Daring Outlaw kicks into play, so you suddenly gain +1 Dodge to AC, but more importantly Sneak attack jumps from +1d6 to +3d6 damage.  A Ring of the Darkhidden (MIC) is a great asset to stealth at this point.

7th: Now you add your Int to damage with the rapier.  Adding the Assassination or Toxic/Virulent properties to your rapier to keep your poisons competitive is a good idea at this point.

8th: Dex gets bumped, adding to your damage, attacks, reflex, AC, and initiative.  If you can use the online addition to SB, you can also use Bluff to seduce people =)   The Ring of Anticipation (DoTU) is a good pick by this point, allowing you to roll 2x for initiative, helping to catch opponents flat-footed.

9th: Craven adds your character level to damage with sneak attacks, so you'll be dealing +4d6+9 (+4d6 +14 against flat-footed) with sneak attacks. 
The Bracers of Murder (DoTU) are a great pick at this point, allowing you to reroll 1's on sneak attacks, as well as gaining +2 to att/dmg against flat-footed foes.

11th: Drow swashbuckler kicks in, allowing you to 5-ft step as a swift action whenever you hit once with at least each weapon in a round.  Or you can keep Acrobatic Charge, but drow swashbuckler is a much more stylish effect in my mind.

12th: You now gain +4 on flanking from swashbuckler, and improved critical with the rapier

15th: Now whenever you critical with a rapier, the opponent is automatically slowed with no save, which should cut down on the mobility of anything trying to do Flyby Attack, or the deadliness of anything with nasty iterative attacks - such as practically every opponent you face by this point.

18th: Now your criticals with the hand crossbow will also slow opponents!  Also, Weakening Critical from SB kicks in, allowing you to deal 2 Str damage to a creature every critical - combine it with 3d6 Str damage from Dragon Bile or another Str-based poison and anything not immune will drop fast.

19th: Swordsage adds nicely to Will and reflex, along with Weapon Focus (Rapier) from Diamond Mind Focus, +1 Init, and 6 maneuvers and a stance.  Blood in the Water stance, Wolf Fang Strike, Sudden Leap, Pouncing Charge, Dancing Mongoose, Swift Invisibility, and Shadow Stride.

20th: Adds Assassin's Stance (or a mobility/senses ones) and probably Rabid Bear Strike.

Character roles and tactics:
The primary role is damage-dealer, which should be strong from 1st to 20th, but really increases in power at 3rd, 6th, and 9th level.  The character is also a strong skills-monkey and scout from 1st-6th, but will be less efficient in that role afterwards due to the SB's mediocre skills list.  The character is also a very solid tank, with 17d10+3d6 HP over the course of 20 levels - and as she gets weaker as a skills character her tanking should improve. 

Finally, the character has more versatility in tactics than most damage-based classes - he can switch between melee and ranged combat easily, and poison use allows him to attack ability scores directly instead of just damage, or deal Con damage along with HP damage to drop a foe even faster than normal.  Ideally, the character will function as the scout and tank, initiating every combat at the front line against flat-footed foes.

In PF, the character can maintain his role as skill-monkey from 1st to 20th. 

Other good feats to take:
Quick Draw (also opens up some skill tricks)
Apprentice (Craftsman or Criminal)

Sample followers:

Human Wizard 1
Stats: let's be optimistic and assume that the follower has a 14 int.
Skills: Craft (Poisonmaking) 4 ranks
Feats:
Skill Focus (Craft (Poisonmaking))
Master of Poisons
Familiar: Sea Snake
Spells:
Magecraft
Items: Masterwork tools
Check: take 10 for a DC 26 poison - enough to create any poison in the DMG except for Dragon Bile and Black Lotus extract.

Human Psion 1
Stats: let's be optimistic and assume that the follower has a 14 int.
Skills: Craft (Poisonmaking) 4 ranks
Feats:
Skill Focus (Craft (Poisonmaking))
Master of Poisons
Spells:
Psionic Minor Creation
Items: Masterwork tools
Check: take 10 for a DC 21 check, enough to magically create a cubic foot of Sassonne Leaf residue (DC 16 to resist, 2d12 damage/1d6 Con).

Human Expert 1 (For games with only NPC followers)
Stats: let's be optimistic and assume that the follower has a 14 int and 12 charisma.
Skills: Craft (Poisonmaking) 4 ranks, Handle Animal 4 ranks
Feats:
Skill Focus (Craft (Poisonmaking))
Vermin Trainer
Items: Masterwork tools
Check: take 10 for a DC 21 check, or take 10 on a handle animal check for a 15, enough to convince a trained vermin to bestow its poison.

Missing books:
Dragon Magazine
3rd party sourcebooks

13. Other:

Ways to lower saves against poisons:
Sickened
Shaken
Hexblade's curse dark companion
Paladin of Tyranny's aura
Blackguard's aura

Ways to possibly increase the DC of poisons from animals/vermin:  (Thanks cru!)
Bear's Endurance, Bite of the Werebear, or other con boosts
Inspire Greatness for more HD

Vermin-related:
Arachnomancer (Underdark): gains spider-related abilities (wizard PrC).
Vermin Keeper (Underdark): Druid PrC that's all about the vermin.
Vestments of Vermin Shape (DMG II, 20,000 gold): lets you wildshape into vermin.
Root-Walker (Dungeonscape): druid ACF that lets you use wild empathy with vermin
Child of Winter (EBCS): lets animal-effecting spells affect vermin, and expands SNA list.
Vermin Companion (EBCS): gives you some crummy vermin companions.
Vermin Shape (EBCS): can wildshape into vermin.

End of the Handbook!

Please feel free to comment, add advice, etc.  This turned out to be a much bigger project than I ever anticipated, and there's plenty of material that I'm sure I've missed!

[Ed-Zero]

As with the original handbook, I love this one

[Libertad]

As noted by Thurbane:

Gehennan Morghuth Iron (Arms & Equipment, pg. 14) is a special weapon material (doesn't have to be magic) that delivers poison with every successful hit.  Its Save DC is low (12) and it targets dexerity (1, 1d4 initial and secondary), but it has infinite uses.  The initial price may be expensive, but it's cost-effective in the long run if you plan on using it often.

[Skyrock]

One addition from Dragon Mag #322, p.37:

Feat: Deep Poisoning
You can trade sneak attack damage to increase the DC of your poisons, up to +5 for sacrificing 5d6.

Sadly you can't use it to outright increase the DC of your poisons as you milk them (the trade has to be made at the moment of the attack), but it could still be useful for certain characters, especially at low levels and when you like to use expensive poisons that would be terrible to waste.