Walking: The Cheapest Way to Move Around: Walkscore can help
I grew up without a car so when I did not ride my bike or took the bus, I had to walk.
As Walk the talk in the August 2008 issue of Ode Magazine states, there is no easier way to cut your carbon footprint than when possible walking around town while running errands, going to a show or eating out.
I am blessed to live in a city, Montclair (New Jersey) where there is a real downtown with stores, restaurants, a theater, a museum and many other amenities within walking distance of my house.
Besides reducing pollution, walking is one of the best ways to keep your weight down and your heart in good shape, just don't overdo it...