Solar cooking
http://solarcooking.org/plans/default.htm?redirect=no
http://solarcooking.wikia.com/wiki/Solar_Cookers_International_Network_%28Home%29
I made the Cook It solar oven (foil and cardboard) with the kids years ago and it works pretty well. Solar ovens use specific pans so make sure you have the proper ones.
http://www.cookwiththesun.com/canning.htm - this guy shows how to home can tomatoes in a solar oven.