I'm a big fan of walking. Done in moderation, for the right reasons and in the right context, walking is a great form of transportation. For example, on a round-trip between sofa and refrigerator, walking is nearly always your best choice.
An ex-colleague is taking walking to an extreme, but in a very neat way. Rich Ambrose has begun an extended walk -- he hopes to cross America on foot. I'm looking forward to sharing the experience (sans blisters, thank you) via his blog: Walkoverstates.