The Great Apes
Gorilla Grodd
Bobo, the Detective Chimp
Sam Simeon
Ultra-Humanite

I've encountered Grodd in the pages of The Flash and on the Justice League cartoon ("Secret Society, Parts I and II"), and I know he was the villain in the first arc of JLA: Classified. The Ultra-Humanite, though in a non-ape body, was the villain in the five-part JSA story "Stealing Thunder" and also appeared in all his white ape glory on Justice League ("Comfort and Joy," et alii). I was introduced to the Detective Chimp in the current miniseries Day of Vengeance, and I can't say I'd mind seeing more of him. As for Sam Simeon of "Angel & the Ape"? I've never encountered him, but then again I've only been reading DC comics for five years.

Hee hee, monkeys.