Paying for electricity to charge your phone is so 2011. In the future, all the cool kids will be hacking their phone charger so they can just leave their phone on the windowsill when the battery's low.  Here's a video tutorial in five simple(ish) steps.

While admittedly you'll still have to order a couple of supplies -- like the little solar cells, or maybe a soldering iron -- the simplicity of endeavor makes it the perfect rainy day project (although, if it's raining outside, then you probably won't have much luck testing the thing).

If the video moves a little too fast for you, there are more in-depth instructions over at the Instructables website. Meanwhile, the poopy-heads over at MetaFilter have picked apart the science for us, offering some alternative suggestions. Now you're just a little chopping, snipping, and taping away from impressing all your friends with your MacGyver-like technical savvy!