Living Social offers the Unu Enerpak Tube 5,000mAh USB External Battery Pack in four colors (White pictured) for $29. Coupon code "AUG10" cuts it to $19. With free shipping, that ties last month's mention as the lowest total price we've seen for this model. (It's a current price low by $16.) It features the ability to extend talk time by up to 15 hours and a flashlight. Note that no AC adapter and no cables are included, but it's purportedly compatible with "all" USB chargers and cables that come with cell phones and tablets.