TechRabbit offers the refurbished Mophie Juice Pack 6,000mAh Powerstation Pro Rugged Portable Battery Pack in Black for $4.99 with free shipping. That's $10 below our December mention of a new unit and the lowest price we've seen. (It's the best deal now for a refurb by $5, and $10 less than buying new.) It features a rubber shell with a stainless steel outer band, USB and microUSB charging ports, and an IP-65 rating for protection against dirt, sand, water, and other liquids. Deal ends May 25.
A 1-year warranty applies, but it's not clear who backs it.