1) Your commute can alter your genes.
According to Dr. Ruth Loos, a program leader at the Institute of Metabolic Science in Cambridge, England “Physical activity, even in small doses, may subvert genetic destiny. You don’t have to run marathons or work out in the gym. Walking the dog, cycling to work, weeding the garden — those all count” and provide enough moderate to vigorous physical activity to reap benefits.
“Physical activity attenuates the influence of FTO variants on obesity risk: a meta-analysis of 218,166 adults and 19,268 children.” PLoS Med.

2) The yearly average health cost savings for a physically active person (30 minutes or more of moderate activity/day for five days a week) is between $305 and $907. 
-Colditz GA. Economic costs of obesity and inactivity. Med Sci Sports Exerc. 1999;31(11, Suppl):S663–S667.
-Wang G, Pratt M, Macera CA, Zheng ZJ, Heath G. Physical activity, cardiovascular disease, and medical expenditures in U.S. adults. Ann Behav Med. 2004;28(2):88–94.
-Pratt M, Macera CA, Wang G. Higher direct medical costs associated with physical inactivity. Phys Sportsmed. 2000;28:63–70.

3) Adults who bike to work have better weight, blood pressure, and insulin levels. (Gordon-Larsen, P., et al., 2009)

4) Women who bike 30 minutes a day have a lower risk of breast cancer. (Luoto, R., et al., 2000)

5) Adolescents who bicycle are 48% less likely to be overweight as adults. (Menschik, D, et al., 2008)

6) The health benefits of cycling outweigh the risks by a factor of 20 to one. (Hillman, M., 1992)

7) Sustainable transportation strategies can increase employee productivity 50% and cut sick time in half.
Research includes: Nieman, David, et al, “Immune Response to a 30-Minute Walk,” Medicine and Science in Sports and Exercise,Jan. 2005, pp. 57-62.  Besser, Lilah, et al, “Walking to Public Transit: Steps to Help Meet Physical Activity Recommendations,” American Journal of Preventive Medicine, 2005, Vol. 29, pp 273-280.

8) Studies have demonstrated a significant link between commute stress and job satisfaction.
Research: Wener, Richard, et al, “Commuting Stress: Psychophysiological Effects of a Trip and Spillover in the Workplace,” Transportation Research Record: Journal of the Transportation Research Board, No. 1924, pp. 112-117.

 *Check out the Case for Cycling wiki for more on why bicycling benefits everyone, not just people who bike.