John Fund has an an excellent guide of where to watch tonight (which includes a nice plug for RCP, btw). I'll be watching two places: Indiana and Kentucky, as previously mentioned, and also upstate New York.

New York features races in five Republican-held seats (districts 20 | 24 | 25 | 26 | 29), of which it's looking like they'll probably lose two: Sweeney in 20 and the open seat in 24. Keep your eye on the results in the other three races as an indicator of the way the rest of the night may go.