Here's my current list of settings that I pull bits and pieces from:
Everquest D20 (races, spells, monsters)
Dragonlance (races, classes, monsters)
Eberron (races, classes, monsters)
Forgotten Realms (races, spells, items, monsters, sites)
Iron Kingdoms (this is the setting that I use as the base of my campaign)
Relics and Rituals: Olympus (races and monsters)
Oriental Adventures 3E (races, classes, monsters, spells, background info)
Scarred Lands (spells, items, races, monsters, sites)
Talislanta (races and monsters)
Warcraft (races, classes, spells, items, sites, monsters)
Dark Sun (races)
Ravenloft 3E (Monsters)
Soveriegn Stone (monsters)
Avadnu (races and monsters)
Call of Cthulhu D20 (monsters)
Warhammer Fantasy Roleplay (mood, sites, Chaos)
Diamond Throne (races, monsters, classes, spells, sites)
Confrontation (monsters, background info)
This is also sprinkled in with various other books like Chaositech, Arsenal, Factory, Manual of the Planes, Planar Handbook, a couple of the Races of Renown series, Mythic Races, the Complete series, the Races of series, and so forth. Not to mention a whole slug of pdf's either bought or downloaded from fansites. It's not your common fantasy setting, but that's exactly how I like it!
Kane