A few time after the 2008 election, Nate Silver started his
Senate rankings : he ranked all the Senate seats up in 2010 based on their estimated likeliness to change hands. I think the forum could make something similar for the 2012 elections. What we would do there is to mentions the seats (open or incumbents) which we expect to switch parties in 2012, and those where we think such situation is possible.
I've also included a poll, so that after posting our rankings we can select the seat swing we expect based on those predictions. The poll will remain open for about two years, and since the situation will certainly change by this time, you can change your vote each time you want. Let's see how good we are at forecasting !