In the supporting races, momentum seems to be with George Clooney and Rachel Weitz. Both have larger roles than their fellow nominees, so that sometimes helps. I do think Weitz is the most deserving; she makes an indelible impression early in THE CONSTANT GARDENER and then once she's gone, you continue to think about her throughout the movie.
Clooney isn't going to win for Best Director or Best Screenplay, so this may be his consolation prize plus he's gotten very good reviews for his SYRIANA work.
However, I'm thinking Paul Giamatti might sneak in here for CINDERELLA MAN. Giamatti failed to get nominated the previous two years for either AMERICAN SPLENDOR or SIDEWAYS, both of which shocked much of Hollywood, so this may be payback time for him, and we all know the Oscars quite often work that way (witness the undeserved wins for Elizabeth Taylor in BUTTERFIELD 8 or Al Pacino in SCENT OF A WOMAN to name just two examples).