IMHO the BEST rechargeable batteries are the fairly new ENELOOP by Sanyo.
The main feature of this new technology [that others are coming out with too] is that the batteries do NOT discharge while sitting unused. Old style nickel metal hydride discharge at a rate of about 10% a week, to where in about a month or two they are totally dead and need to be recharged.
The Sanyo ENELOOP batteries discharge at about 10% to 20% a year, and down to about 70% power after two years. So you can put these in a flashlight, radio, or whatever and not have to worry about these going dead when sitting unused.
Check out Wikipedia for info on these. [See below link.]
Costco had a special on them, but they are now on a side aisle there [I bought three more of the kits at Costco last week.] They come in a blue plastic box, with a charger, C and D adapters, 8 AA and 4 AAA batteries, all for $25 [at Costco].
I bought 8 of these kits simply to get the batteries. [on eBay the batteries were more expensive than the kit. And on Amazon the kit goes for about $35 shipped, if not more.]
I replaced all my batteries with these and only have about 12 left over. Guess I use more batteries than I thought.
I have them in my two Wii remotes and they work very well. And as a bonus, they match the Wiimote!
I also have them in my digital cameras, which require more "powerful" batteries, so to speak. The ENELOOP have worked very well in my cameras, despite the rating of the AA battery being 2000 mAh [cameras like 2200 to 2400 mAh rechargeables, but I have found these ENELOOPS last just as long as my 2400 mAh rated batteries. Not sure if it's the new technology, but they work very well and that is all I care about.]