Though that I only know him as "Dude from 4 Months, 3 Weeks & 2 Days" probably doesn't say much for his Oscar hopes (impossible as they are). Male supporting-wise, I also liked Ralph Fiennes in In Bruges, but that entire movie will probably go overlooked at Oscar time and Fiennes' role can't really compare with what Ledger was given. So, yeah, he's in my top spot, but it's only July, as has already been stated.

(BTW, the less we talk about Cassandra's Dream the better.)