Go through all the songs you have on your computer and pick out ones that make you want to lipsync and dance around the room (since they're so much fun). Make a playlist containing those songs and play those while you workout. Don't stop there, keep that list up to date so you don't get bored.
Now if you wanna get technical about it, you could download a shareware program like beatunes and have it analyze your music so you can add in the BPM (beats per minute) per song. Using that, I made a more precise list of song I love and have a high BPM. Mine ranges from 110-210 BPM.