Since my digital camera requires two AA batteries to operate, I find myself constantly replacing them. It seems that the camera uses so much power that the AA batteries don't last long enough to be practical. I decided to by lithium batteries which extended my camera use a bit longer, but I was still annoyed that I had to replace these expensive batteries sooner than I wanted to.
I finally purchased the Digital Concepts 1 Hour Battery Charger, that came with 4 AA rechargeable batteries. It is capable of charging 2-4 batteries at a time, and includes two adapters, one for an outlet, and the other will charge in a power port, or cigarette lighter for when you're on-the-go. Nice touch! Not only does it charge AA batteries, it also will charge AAA batteries as well.
The claim is that it will charge batteries fully in an hour, which it did. However, when it finished the job, I found that the unit was slighty hot, so it would be a good idea to put this someplace that's not flammable during the charging mode. I DO like the fact that I will have batteries when I need them for my camera, without having to run down to the nearest drugstore at the last minute.
Other than the heat coming out of the charger, so far it's been a reliable unit.
Update On Apr 17, 2008: Now that I've use the battery charger for a while, I find that the rechargeable batteries may not last as long as the lithium batteries did, but since the kit came with 4 AA's, and my camera only uses two, I always have a backup.
I also discovered that it has a "bad cell" detection when the rechargeable batteries are no longer usable.
As far as the heat coming from the charger... that seems have lessened the more I've used it. It still gets warm, but apparently there's some sort of thermal cut off so as not to damage the battery by overheating.