I have long thought that Richard Posner should win the Nobel Prize in economics (see here for the reasons I provided nearly 6 years ago); I keep a reminder of this at the top of this blog. For all the reasons cited there, I am still willing to make the case, but his flirting with neo-Keynesian macro in the past couple of years has dampened my enthusiasm somewhat.
One of my friends says that Oliver Hart and Richard Thayler are the leaders in the futures markets, where people try to predict (and bet real money on) who will be awarded the various Nobel Prizes. I can easily imagine that Thayler might be a popular choice, given his work on behavioural economics, which has gained much more favour during the past two or three years. But the Nobel committee does not always seem to like the popular, easy choice.
Aside from Posner (who would be a long-shot at best), other candidates surely must include Jagdish Baghwati for his work in international trade (I think I mentioned him last year, too); and another strong candidate should be Gordon Tullock for all of his inspirational work on the economics of public choice.