Any alchemical, pyrotechnics feats...

[NevinPL]

...sans Grenadier(PHBII) ?
Something that will help Alchemical Fire, Tanglefoot Bag thrower.
No Eberron, and preferably no PF.

[Firest Kathon]

From Pathfinder: Throw Anything (http://www.d20pfsrd.com/feats/combat-feats/throw-anything-combat---final), +1 on attack rolls with thrown splash weapons.

[ShurikVch]

Mad Alchemist - [Tactical] feat from the same PHII (with Grenadier as prerequisite)

Pyro - in Song and Silence

[Grod_The_Giant]

I see no reason why you shouldn't be able to use Power Throw (Complete Warrior) to power attack with alchemist's fire and the like...

[daremetoidareyo]

Shaped splash from races of eberron:

"If you throw a splash weapon and it hits the creature you target, you can immediately make a second attack against any creature adjacent to the first. If the second attack succeeds, the secondary target also takes direct hit damage from the thrown splash weapon." Plus the ability to not do splash damage to your friends.

The text of the feat implies that you only get a single adjacent target, but this limitation is not explicit other than the use of ordinal words associated with targets; "first" and "second." You might be able to get direct damage on an entire hoard of enemies if your DM is RAW to a fault.