Duracell 2650 mAh AA Rechargeable 8-Battery Pack is available for $9.99 at OfficeMax. Buy 2 packs plus a small eraser or something for a few cents and use the coupon here to take $10 off $20 to get 16 AA Duracell batteries for $10. Find a location near you here.
Originally posted earlier, this is a friendly reminder. This post has also been slightly revised.