BuyDig offers the UNU 14,000mAh Enerpak Extreme Dual USB External Battery Pack in Black, model no. EP-02-14000BS, for $35.99 with free shipping. That's $19 below our mention from last year and the lowest total price we've seen. (It's a current low by $15.) It's compatible with most smartphones and tablets and features 2.1-amp output and simultaneous dual charging.

Update: The price has dropped to $29.