I use the Sanyo Eneloop ones they seem to do the job pretty well
I second, Third, or Fourth this selection. Better than ANY rechargable I have ever used. Hold a charge a long time when not in use so they are ready to go. Use them in my Gigapan as well as my flash. In the Gigapan a set will far exceed the life of the best set of throw away batteries by almost 2 to 1 life.