Riddle me this: what is better than one big honkin' external battery? Yes, two big honkin' external batteries. If you head over to Amazon right now, you can get two New Trent batteries at quite a discount. In this age of non-removable smartphone batteries, how can you lose?
All you have to do is add the New Trent iCarrier and iGeek batteries to your cart. Then use the coupon code J8F6EA63, and you'll get the $59.95 iGeek for (almost) free. The iCarrier sells for $76.95 and has a 12,000mAh capacity. The iGeek is smaller and more portable, but still packs 9,900mAh of juice. If all goes as planned, you should only pay $77.55 plus tax and shipping for both batteries.
These batteries should work with all your Android devices, and plenty of other stuff too. This might be a one-day sale, so make a call quick. The coupon has been confirmed working as of this posting.