I used to use Hahnel, but they are actually slightly fatter than standard AAs and the battery case I had wouldn't take them. Plus they drained like crazy.
I now use Energiser 2500mAh and Duracell 2650 mAh AA rechargeables.
The Duracells seem to last forever in my Canon camera (takes 2)! Better than the Energizers! I charge them all in an Energizer 1hour battery charger, which has individual charging for each cell - so you can mix empty and partially charged batteries.