Double USB Charger by Gametech. This simple device is just a box with 4 AA batteries in it, and two USB ports on the side. It comes with a bunch of adapters so it can be used to charge the iPhone, 3DS, PSP, and various DSes.
And when you aren’t charging two items at once, it collapses into a tiny little rectangular box. Kind of a nice design!
See also: More accessories