Consolidated Lists from WotC: Classes, Prestige Classes, Feats and Monsters!
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Check out this new article Wizards of the Coast posted recently:
Consolidated Lists -- Wondering where you read about that prestige class? Check out our consolidated indexes from D&D published sourcebooks. Keep an eye out for future indexes, as well as revised indexes once new sourcebooks have been released.
Consolidated Lists: Character Class Index
Consolidated Lists: Prestige Class Index
Consolidated Lists: Feat Index
Consolidated Lists: Monster Index
Consolidated Lists: Invocations
Consolidated Lists: Spells