USBCell - Rechargeable USB Batteries
This is simply brilliant. The USBcell from Thinkgeek is basically a rechargeable (Nimh) AA battery, which as the name implies, can be charged by plugging it into any computer USB port.
Snip from the site:
Now, when your batteries are flatlining, pop the cap, and jam ’em into your nearest ubiquitous USB port. Whether it’s on your computer, laptop, monitor or powered USB hub, all you need is 250mA of juice from your universal serial bus, and a little patience. In just a few hours, you’ll have 1300mAH of power!
The USBCell is a complete steal at $19.95 for two AA batteries.