I got a $20 unit that plugs into the wall, or 12V cigarette lighter plus. The unit charges 2 or 4 AA or AAA batteries. It came with 4 AAs of decent capacity. (I use them in my bike's ipod speaker.)
http://www.walmart.com/catalog/produ...uct_id=5640639

I like the wal-mart unit because I can charge it from 12V with my small off grid solar PV power plant without using the inverter.

I charge my Ipod, and my headlight's 7.2Volt pack, as well as all of my AA and AAA batteries via 12Volt solar power. My bike is totally OFF THE GRID!