I have seen several different gadgets that are intended to charge up cell phones and MP3 players from simple batteries you connect to extend the life of your phone, to solar recharger's.

A company from England called Orange teamed up with the University of Texas, who ironically are also orange, to develop the first wind powered cell phone charger. The charger looks like the larger wind turbines that we have been hearing much of lately.

This small version however, looks more like a child’s toy than a gadget charger and the device weighs 150g. the makers say that it is intended to take advantage of the British climate (presumably it is quite windy there) and be attached to the top of a tent where it captures power all day to charge a phone at night. I guess you could trick your kids into thinking it was a pinwheel, thereby having them blow on it for hours on end so you can make a call to the babysitter. via Ubergizmo