Funny how all five of your good chances are Democrats. Well, it's not funny so much as inaccurate and biased. Having five in the top might be a bit over the top, yaddamean?
Franken is the best chance, followed by Hagan and Begich, perhaps. I suppose Risch and Johanns are safe, but I expect one of the two not to run for reelection.
edit: on reflection, I dunno about anything I just said
That is because the 2008 senate elections have resulted in more freshmen Democrats than Republicans. As I have already noted, there are only 2 new Republicans as opposed to 8 new Democrats.