I like to walk for exercise, but tend to stroll if I don't have a beat to follow. So I looked for fast music and finally found a website with cardio music mixes, about an hour long each. http://www.djsteveboy.com/podrunner.html
All the archives are available free, they are in MP3 format, and tell you how fast they are in beats per minute (BPM), which I found very helpful. The DJ makes new ones every so often, and has quite the collection of music. He asks for a donation if you can manage it, but doesn't require it at all.