BigDeals via eBay offers the Monoprice 2,200mAh External Backup Battery Charger for iPhone 3/4 for $5.99 with free shipping. That's tied with our mention from two weeks ago, $14 off list, and the lowest total price we could find. It's compatible with iPod Touch, iPod Classic, iPod Nano, iPhone 3, 3G, 4 and 4S.