Denver is blessed with amazing central neighborhoods. I live in a house with a yard and the whole bit. Yet I'm 11 minutes by bus to Downtown. I generally ride my bike to work (we have an amazing intra-city bike path system) or take the bus. Because Denver is so incredibly compact getting around without a car is easy.
Our neighborhood has lots and lots of restaurants, coffee shops, dry cleaners, etc... so we almost always walk when we go out.
Point being: Denver certainly fits the bill.
It's also rather affordable. I'm a huge fan:)