Humans power is pretty good stuff, for a long long time it was the only form of power that we could count on. With that in mind I present, The hand crank cell phone charger. (Japanese site)

This bad boy will work if the sun it out, or if you are in a cave. So long as you can get enough room to run that crank. Its a good idea, we should use human power more often, keep us from getting fat. (did I mention it also comes with a flashlight?!)