I might be the only one into this but I like to listen to...
electro -- The Faint, Peaches, Tracy + The Plastics
punk/emo -- Alkakine Trio, Green Day, Rocket from the Crypt
Brit pop -- Libertines, Arctic Monkeys
I like to listen to stuff that is really fast since I do a lot of cardio. Faster dancey music helps keep me going and pushing myself to go faster.