Running

http://www.furman.edu/first/

http://www.mcmillanrunning.com/mcmillanrunningcalculator.htm

Biking

http://www.abc-of-mountainbiking.com/

http://sheldonbrown.com/

Triathlon

Turbulence Training

http://fitnessblackbook.com/recommends/turbulence-training-videos

General Fitness

http://www.shapeupamerica.com/2008/04/18/web-based-exercise-and-fitness-tracking/

http://mashable.com/2008/11/25/vote-for-best-fitness-site/

http://thetrainingstationinc.com/exercises.html