FWIW, someone else brought up rechargeables, and mentioned the "strength" of them.
If you purchase rechargeable batteries, look at the mAh of them. General purpose batteries are in the 1600-1800 range, which will be useless a lot quicker than something in the 2000-2400 range. The higher the range, the better it is for things like a camera, which used the greater capacity to fire off your flash without draining your batteries as fast.
Using them for other things that don't seem to require as much juice instantly seems to last about the same time.
Examples - Walkman or Portable CD player, batteries seem to last about the same amount of time fully charged.
Cameras or Remote Controlled cars - higher numbers seem to equal longer usage.
Oh, and make sure you can pick up a camera bag that will hold that camera and the charger/spare set of batteries. Much to my wife's chagrin, she forgot to charge the batteries on our trip, and was VERY pissed when we had to pick up a few disposable cameras to take pictures instead of our handy dandy little digital camera!