Here is an online casino's odds for the next Supreme Court Justice nomination:
Sonia Sotomayor 13/8 (Favorite, less than 2 to 1)
Diane Pamela Wood 9/4
Elena Kagan 4/1
Kim McLane Wardlaw 9/2
Kathleen Sullivan 8/1
Another comment to add on Wood, other than my comments below, is that she is an elitist from Chicago and probably runs in the same circles that Obama did/does.
Interestingly, Wardlaw has been getting a few mentions. She is the best possibility from the list, meaning the most moderate. She ruled in favor of displaying the 10 Commandments on public property, ruled against habeus corpus for detainees, and gave the EPA a broader scope in one ruling. She is hispanic on her mother's side and was the first female hispanic named to the court of appeals. She worked in the Bill Clinton presidential campaign which might hurt her even more than her moderate rulings.
Post Note 5/10: Here is a site that claims Obama and Wood have a personal relationship when they both taught at the University of Chicago law school.