Clickfree is a company making some interesting and simple USB-based backup products, and their latest Transformer for iPod/iPhone may be the most clever yet.
Their theory is that you have a lot of unused space on your iProduct. You can just connect your iPod to your PC or Mac through their $US50 cord, and it will load integrated software to automatically backup selected files.
They promise to only utilise the unused space on the device, leaving all of your music and contacts safe.
The other, not so advertised function, is that the Clickfree allows you to download any MP3s off an iPod to a computer and one-button transfer them into iTunes.