Last year, due to rising gas prices, I started biking to work about three days per week. Acutally, I do a bike-bus combo commute.
It is beautiful, and I love it. But the funny thing is that, even though I started doing it to save money, by the time I pay the bus fare, it actually doesn't save much. I figure that just in gas, I save only about $1.00 per day. Since I do the bike-bus commute 3 days per week, it adds up to only about $12 per month. And since I only do the bike-bus commute in the fall and spring (winter the trails are icy and summer school is out - I'm a teacher) it adds up to only $66 per year. I pay almost that much getting my bike tune-up each year! And I had to buy some things to outfit my bike for commuting in the first place: fenders, lights, a new chain, a rear rack and basket, etc. So overall, at this point, I think biking has actually *cost* me money. (Of course, it probably isn't fair to include my bicycle maintenece figures in that analysis, and not the car maintenence, but still...)
I still do it though, more because I am just in love with being outside, riding along a beautiful trail so often. Even in the rain, it is such a gift, and makes me feel very rich and fortunate. I figure: I am paying the money anyway. Why not pay it to support an activity I love and that brings me such pure joy, rather than pouring it into my car??