I give a hearty second to the
La Crosse BC-9009 (formerly the BC-900) recharger, and it can charge any brand of rechargeable NiMH and NiCad AA and AAAs one, two, three at a time or all at once and all at different rates. It also has a mode to restore the capacity of older batteries. I used to have an Energizer 15-minute charger, and after it burned out
plus greatly reduced the capacity of some of my AAs, the La Crosse has been a God-send PLUS it was little more than half the price. (The faster the charger, the hotter the batteries, and therefore the lower the battery capacity over time. The Energizer 15-minute charger gets 'em pretty hot!!)
However, I have the K20D so I don't need rechargeable AAs for that, but in my flash I use Energizer AA lithiums. Sure, they eventually die, but only after hundreds of shots; they simply outlast any other type of battery (alkaline, NiMH) and they're very lightweight. Plus, they recharge your flash
insanely fast!