Chris Sims beat me to the punch on one of Batman's most ridiculous villains, giving a great rundown on Orca, the crazy marine biologist in an improbably realistic homemade whale costume. I couldn't do as good as writeup as Chris, so just go to the ISB
After The Scarecrow, Ra's Al Ghul, The Joker, and Two-Face, who should be Batman's next enemy in the Batman Begins/The Dark Knight series? Well, as of now we know that Tom Hardy will play Bane and Anne Hathaway will play Catwoman.
Check out the master list for all the villains covered. I've pretty much run out by now. Obviously, there are more Batman villains, but not any of significance that I know of. As of February 2009, no one is confirmed as a villain. Not the Johnny Depp Riddler, not Phillip Seymour Hoffman Penguin, nobody.