If you're looking for a nice portable battery pack to carry around. Anker has a nice 12,000mAh battery pack available for $50 which is about 50% off the normal price, but it doesn't stop there. There is a coupon code that you can use to get an additional $10 off. Using the Promo code ASTRO32G you can get the Anker Astro3 portable battery pack for just $39.99. However, there is an alternative here. You can get the Anker Astro Mini 3000mAh battery pack for free, if you buy the Astro3 for the regular $49.99 price. Both are pretty good deals. However the coupon codes for the Astro Mini depend on the Color, for Black you'll need the ASTROB3K coupon code, ASTROS3K for the silver one, ASTROP3K for the Pink and ASTROU3K for the Blue version.
Both battery packs are relatively good, considering they are from Anker, they are really good actually. The Anker Astro3 has three USB ports so you are able to charge three devices at once, it also has LED indicators to show you how much battery life is left on the battery pack. For those interested you can buy the Astro3 from the links below.
[Upgraded Version & All Smart Port] Anker® 2nd Gen Astro3 12000mAh External Battery Fastest-charging (4A Output) Charger for iPhone 5S, 5C, 5, 4S, iPad Air, 5, Mini 2, Samsung Galaxy S4, S3, Note 2, 3, Tab 2, 3, Google Nexus and more (Apple Adapters - 30 pin and Lightning, Samsung 30 pin adapter, not included)