Toy Story 3 is the obvious winner this year unless the Academy decides they're not going to be snobs and just hand it the Best Picture award (chances: less than 1%), in which the Best Animated Feature can go to something else.
How To Train Your Dragon looks like it'll be Dreamworks' champion. Shrek Forever After and Megamind I don't see being pushed very much.
The 3rd slot is up in the air. It could be anything. Summer Wars or The Illusionist for the "foreign artsy" factor, plus to keep the nomination from being too CGI-dominated, both have a shot. Then there's Despicible Me which Fox is going to push HARD. The Illusionist's director snubbed the Oscars when his last film got nominated though so that might hurt The Illusionist's chances with the egomaniacal Oscar crowd.
EDIT: Now Cartoon Brew's comments are spreading rumors the Academy may expand the slots to five anyway. I'm confused.
EDIT 2: Never mind on the rumors, they've been disspelled by the source. Eee.
One final statement: I will admit I have bias towards Summer Wars and The Illusionist because I want the jaws of Pixar's and Dreamworks' executives to slam into the Oscar red carpet in the most comically epic fashion humanly possible.