If you're still hooked on disposable batteries, there's no better place to buy them than Costco.  Their Kirkland brand batteries cost a fraction of what Duracell batteries do, and perform just as well.  But if you're ready to take another small step towards living greener, buy rechargeable batteries.  Rechargeable battery technology continues to improve (they power CARS now, for goodness sake) and the best-of-the best, Sanyo Eneloop just got better.  A four pack of Sanyo's new 1500 eneloop Batteries costs about $10 at amazon.com, and they come pre-charged, so you can use them right out of the package.  You'll also need a battery charger — I still love the La Crosse Battery Charger I wrote about two years ago, but if your battery needs and/or budget are limited, you can buy 4 Sanyo eneloop batteries with a basic charger for about $20 including shipping.  If you're using your batteries in high-drain devices like a digital camera, you might do better with the eneloop XX batteries.  They offer longer-lasting performance between charges, though fewer cycles of use before they need to be replaced. If your battery needs include C- and D-sized batteries, you can get adapters that allow rechargeable AAs to fit in C- and D- sized equipment.  They came with the La Crosse BC-9009 that I have, and you can also order eneloop adapters online.