Generally, I like upbeat music with a beat to exercise to. Something to step into. It can be slow, and I'll take two steps per, but it should be zippy. Dance music (and Drinking Songs) are good for this sort of thing.

I'm not a big Deadhead so I'd get tired of them after a song or two, but when they're on they're on. I can wallow in Weird Al/Luke Ski's weirdness as well, taking my mind out of the physical act while limbs move.