In my opinion, these should have been the nominees:
Steve Carell, Little Miss Sunshine
Jackie Earle Haley, Little Children
Danny Huston, The Proposition
Jack Nicholson, The Departed
Ray Winstone, The Proposition *WINNER*
For those of you who haven't seen The Proposition, see it. Winstone and Huston pretty much blow away any supporting performance that year. It's a damn shame so few people saw the film. As for the actual nominees that year, Haley was the clear winner.