Music is the great fitness motivator, and the faster the beat, the faster you move. If you're looking for an entire playlist that offers non-stop, fixed tempo music for your running, walking, or cycling workouts, check out Podrunner.

The site offers free workout playlists to help keep your pace constant, with ranges between 152 to 181 beats per minute. Podrunner also has mixes designed for interval training. You can download these music mixes online or through iTunes, and the MP3 files can be played on most digital music players. The playlists are all electronica, and the music is energetic and upbeat. Best of all, it's free.