Depends.
If I'm road running, I like "Cuban Girls", by the Black Eyed Peas.
Trail running, I like upbeat redneckish country, like "John Deer Green" by Joe Diffy, or "indian outlaw" by Tim McGraw.
If I'm lifting, I like "The Enemy", by Godsmack.
If I'm mountain biking, I like "Soweto", by Hieroglyphics, and also "The Distance" by Cake.
Road biking, I like "Lie in our Graves" by Dave Matthews Band.
Jumping rope, I like the Quake game sountrack by the Nine Inch Nails... it's rock instrumental with the same beats over and over.