Although they’re nearly twice as expensive as traditional rechargeable batteries, the USBCell from Moixa Energy can be recharged via USB, so if you keep your computer on most of the day, might as well use those extra USB ports to charge the batteries instead of spending extra for a battery charger.
Currently, the only USBCell available is the AA size, but Moixa also plans to sell AAA, 9-volt, and phone/PDA battery versions in the near future. You can buy a pair of AA USBCells at Amazon for about $19 (USD).
[via Devicepedia]