Want a cheap gadget to extend your battery charge of any USB powered portable device like an iPod Shuffle or a phone? This hack from Hackaday
is as simple as it gets if you want to build yourself a USB battery. All you will need are 4 things - a 5.1v Zener diode, 100 ohm resistor, 9v battery & connector and a female USB connector. Needless to say a little bit of electronic soldering ability or friendship with a geek who can make one for you will also be needed.
Pretty slick idea in our opinion, and you can't beat the simplicity of the project.