Brad Pitt in Tree of Life & Patton Oswalt in Young Adult reaped four nods each, while Nick Nolte & Andy Serkis each got three nominations for Warrior & Rise of the Planet of the Apes, respectively. Jonah Hill (Moneyball), Max Von Sydow (Extremely Loud and Incredibly Close) & Armie Hammer (J Edgar) show up lower down the list with two nominations each.
The critics' favourites seem to have translated well to the more formal awards; Christopher Plummer is the clear front runner with six nominations and two wins, while Albert Brooks and Kenneth Branagh clock in with four each. Brooks missed out on the very important Screen Actors Guild nomination, however, but the very thorough critical attention should secure his place. After them, Jonah Hill and Nick Nolte clock in with three nominations each, and that is likely to be the final five.
All the attention for Brad Pitt has been redirected to Moneyball and, especially as Tree of Life has been very underwhelmingly received by the major awards bodies, it seems fair to think that he won't manage a second nomination for Tree of Life. The whole Andy Serkis campaign regrettably hasn't taken off with the mainstream awards, and particularly with the important Screen Actors Guild, so I'd count him out (actual filmmakers & actors still seem less enchanted with motion capture than the critics).
So, my predictions:
Christopher Plummer - Beginners
Albert Brooks - Drive
Kenneth Branagh - My Week with Marilyn
Nick Nolte - Warrior
Jonah Hill - Moneyball
Max Von Sydow - Extremely Loud and Incredibly Close
Patton Oswalt - Young Adult