If you're in the mood for a geeky project, you can purchase a kit that includes all the electronic parts necessary to build your own MintyBoost: a small and simple (but very powerful) USB charger for your iPod (or other MP3 player), camera, cell phone, and any other gadget you can plug into a USB port to charge.
This project is suitable for beginners, some soldering tools are necessary but even if you've never soldered before it should be pretty easy. When you're done, the charger circuitry and 2 AA batteries fit into an Altoids gum tin, and will run your iPod for hours. You can use rechargable batteries too. What's this all about? read more
The kit, $19.50, has been tested and works with: iPod nano/mini/photo/video/shuffle, Blackberry, iPaq, LuxPro Tangent, Rio Carbon and Samsung T809. Apparently, if you get the right cord set up, you also use it for your Nintendo DS.
For more info, check out the Minty Boost website.