John Saves Energy - a website that shows how one guy came to power a house and two cars with solar power and other energy efficiencies. Would love to be energy independent one day. Also a news story about it here: http://m.ksl.com/index/story/sid/30560444?mobile_direct=y
This works even on cold and relatively cloudy days. It can be useful for locations with hot summers and cold winters, switching between cooling and heating by adjusting which vents are open and closed.