I am a year-round bike commuter who lives and works in
Savings. I avoid approximately $1,500 per year in car related expenses. These are the cost related to gas and normal maintenance. And heck, I do not need to pay for a health club membership.
Health hazards. Exposure to traffic congestion increases heart rate, blood pressure and negative moods.
Long, arduous commutes to work, air pollution and a sedentary lifestyle are unhealthy. Through bike commuting, you will likely find you are sick less often and are more productive and alert.
Environment. By biking, I reduce my personal contribution to air pollution by over 2 tons per year. My car is one of the cleanest gas powered cars on the road, so your savings may be much greater.
Parking. You get to park wherever you want.
Commute Time. It only takes me on average 10 minutes longer to get to and from work if I bike, rather than using my car. The commute time is almost equal during the winter when I would normally have to scrape or clean off my car. I should note that this is a 8 mile commute each way.
Support. There are tons of mailing list and message boards for peer support with regards to bicycling and commuting in particular. One of my particular favorites is www.bikeforums.net.
Remember, every day spent commuting by bike is an adventure.