Terracotta Pot Candle Heater - Hacked Gadgets – DIY Tech Blog - great forum discussion on how and why they work. You'll be happy you made a couple of these in an emergency. They won't heat your whole house of course, but they'd take the chill out of a bedroom or small room.
Build your own portable solar power generator to take with you on camping trips or for use in an emergency - $150 inexpensive parts from Amazon.com. #environment #technology #diy #green #sustainability