My vote is for Adrien Brody. Terrific actor, and he has a very animated face. Plus he's still very young, so if Warner Bros. wanted to bring the Joker back for another Batman film beyond the next one, they could do that.
And I think he's flat out a better actor than Crispin Glover. He could take this character to levels of psychotic complexity and not just be "crazy evil". Plus Brody as an Oscar winner is more of a "name" than Glover, and the Warner Bros. suits would probably prefer that, not to mention I think Nolan would prefer that as well. He's one of the best young actors in Hollywood, but he's not too "big" either, so it would be in line with the rest of the Nolan Batman cast.
I actually didn't like The Joker all that much in the animated series, I think they could do something darker and more twisted for the BB sequel.
Here are some pics. If you watch "The Jacket", you'll see more of Brody's "crazy grin" but this is the only pic I could fine online of him grinning. He has the perfect hair too.



Come to think of it, his Jacket co-star, Kierra Knightley wouldn't be a bad Harley Quinn ...
