There are a bazillion companies selling external battery chargers for the iPhone and other USB enabled devices. This power packs are really convenient when you’re away from your computer or a wall outlet and your favorite gadget is low on juice. But it seems like most of them are pretty bulky and expensive. I just spotted the Lenmar PowerPort Mini USB Any Where Charger for the iPhone and it looks like it might be a nice alternative. It can offer an additional 600mA of power in a small package (2.2 x 1.4 x 0.4 in). It can be found at Amazon for less than $14.