This episode of Tinkernut shows you how to adjust music by time and BPM to create the ultimate playlist.
Tangerine (Mac): http://www.potionfactory.com/blog/2006/10/18/introducing-tangerine
Taps Per Minute: http://www.all8.com/tools/bpm.htm
Audacity – http://audacity.sourceforge.net
Best Music For A Workout (Article): http://www.nytimes.com/2008/01/10/fashion/10fitness.html?_r=1
How to create the ultimate workout playlist (Article):