The Kensington Portable Power Pack for Mobile Devices is a little charger about the size of a money clip. You power it up with either the included USB AC adapter or through a USB slot on your PC.

The Power Pack charges any mobile device that accepts mini USB. Kensington reports that the device can get you an extra 55 hours of iPod music time and 14 hours of iPod video time. Though I did not test with an iPod, I was able to charge two flash-based MP3 players fully, without putting a dent in the charger's battery life.

The Power Pack has a handy pushbutton that gives you the battery charge status on a blue LED readout. Because the Power Pack is only USB, it is more practical for MP3 players than for most cell phones and PDAs (though you can buy adapter tips for various cell phone and PDA models). I've looked at a few universal battery solutions for charging mobile devices or laptops (or both), and so far, this one has the smallest, sleekest form factor for a mobile-only charger. And at $59.99, the price is about in the middle of the spectrum.