Beyond even building a solar power generator, and ready to hit the roof? No problem—you can install some this weekend using materials from eBay. You can find and buy damaged solar cells on eBay, refurbish them, and turn them into rooftop panels that generate supplemental electricity for your home. You can build a panel for as little as $100. It'll take a few of them to be able to generate enough electricity worth using in your home, but you could turn it into a great multi-weekend project.
We also have instructions for how to mount solar panels on your roof for after you've finished up your homemade panels.