Check these out:


USBCells are standard-sized AA batteries whose heads flip open to
reveal a USB plug; plug them into your PC and they’ll recharge off the
USB port. I already use USB chargers for my phone and music player and
GPS when I’m on the road — this completes the picture. I wish that
every rechargeable device came with a USB recharge point!

Link: http://www.boingboing.net/2006/09/20/aa_batteries_with_bu.html