NIMH rechargeable AA batteries - Chicago Electric.
If you take a lot of pictures with your digital camera, these are a must have.
These batteries are compatible with the Rayovac charger I own and just happened to be located next to the checkout aisle at Harbor Freight (ever notice that's always where they put the batteries?). I've only charged these batteries a couple of times but they charge just as fast as the rayovac's I've been using and seem to hold a charge as long also. How's that for a highly detailed, scientific product evaluation?
They work. That's enough for me.
$2.99 per 4-pack at Harbor Freight.