I've been thinking of a soda can home solar heater for a few years, but like my greywater recycling project, keeps getting delayed by my need to post obsessively on forums ;-)

http://www.treehugger.com/solar-technology/how-build-diy-solar-air-heater-old-soda-cans.html

Wait for it...

https://old.reddit.com/r/therewasanattempt/comments/pvsbdu/to_cook_using_the_power_of_the_sun/