We recently featured one way to heat your house with the sun, but DIYer Daniel Strohl has spent three years perfecting his homemade solar garage heater, made out of a wooden box, some vacuum parts and a lot of empty soft drink cans.
The basic premise of the project is to build a simple box out of some 2x4s, stack a hundred or two black-painted soda cans inside with some adhesive, and stick a vacuum hose on the end to direct heat into your house. You'll also need to drill a hole in the bottom of each can to direct the heat through the box, so a drill press or something similar would come in handy (since you will have to do it 180 times). Other than that, you shouldn't need any other fancy tools.
It won't heat your whole house, but it will do a pretty good job keeping your garage, greenhouse or other small area warm. Daniel's post doesn't give a ton of details on the new version, so be sure to check out his original post (as well as the hundreds of comments below it) for more details on the building and tweaking that went into version two. And, of course, let us know your DIY heating tips in the comments.