Right now you can score some sweet savings on Kmashi's portable battery packs at Amazon with a coupon code. For as little as $9 you can grab a 10000mAh power bank to charge your favorite gadgets while on the go without tethering yourself to a wall. The batteries are rather small and high capacity, with both 10000mAh and 15000mAh units available. Both have two USB outputs to charge multiple devices at the same time if needed, and recharge via microUSB.
These two are currently on sale with coupons:
If you find yourself needing extra power during your day, you will want to have one of these around. At these prices, you may want to pick up some gifts for others as well. Be sure to act quick, as this deal likely won't last long.