This project describes how to build a hand crank Lego usb charger with parts from a Mindstorms kit and Radio Shack.
The charger uses a Lego motor to generate current which is passed through a voltage regulator and then to the usb port.
It would make a great stocking stuffer for anyone who uses devices that charge via usb. If you are getting it for a person who likes to build their own things, just collect all the parts put them in a ziplock, and put that in the stocking. Then when they want to build it you can show them this instructable.