With appropriate tools and a spare iPod or USB cable to cut up, you can make something that can power any USB device out of a 9v battery. You need something to limit the voltage to 5 volts (I forget what it's called, but it's at Radio Shack), but it's really handy to have in your pocket when you need to power a Nintendo DS (not a USB device but can charge off USB current), iPhone, iPod, or camera for an hour or so.
I bought my dad all the parts he'd need to make his own, wrapped them in a box, and gave it to him for his birthday. I hope he figures out how to put it together by May.
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As for your iPod, I would recommend you get the battery changed in it. You can do it yourself for $40. If it's in warranty you can send it to Apple for free.