The New York Times Magazine for this Sunday was all about "going green," and it listed ideas for helping the environment. Walking more, instead of driving, was one of the main actions it listed that could help reduce your "carbon footprint" (I hate that phrase).
In the article, it listed a site called walkscore.com, which tells you how "walking friendly" (sorry about all of the "quotation marks") your neighborhood is, judging by how close you live to necessary locations like grocery stores, restaurants, parks, etc.
My house gets a 55, which means my neighborhood is very walkable. The site said 50-70 means "Some Walkable Locations: Some stores and amenities are within walking distance, but many everyday trips still require a bike, public transportation, or car."
My old house got a 14. Scores from 0-25 mean "Driving Only: Virtually no neighborhood destinations within walking range. You can walk from your house to your car!?"
You can check your walkscore at walkscore.com