I just gave out the my first campaign contributions of this cycle -- to Tom Perriello, Vic Snyder, and Mary Jo Kilroy. All 3 are vulnerable Democrats from fairly conservative districts who voted for the stimulus bill, cap & trade, and health care reform.
You can see Nick's data on how much more liberal they are than their districts here. Kilroy is the 154th most liberal congresscritter, and she represents the 192nd most liberal district. In other words, she's moving her district 38 places left of where you'd expect it to be. Perriello has the 247th most liberal voting record in the 261st most liberal district. (I also like the fact that he co-founded a pretty awesome international human rights organization before going to Congress.) Both of the above two candidates are vulnerable first-term representatives, so they can't be expected to perform at Vic Snyder levels of heroism -- 117th most liberal in the 249th most liberal district.