If you have an old iPod kicking around, TechHive has some ideas that'll help you breathe some new life into these vintage devices. Each upgrade mentioned in the post are warranty-voiders, but that doesn't matter anymore because the devices are so old.
The lists of mods include changing the backlit LED, swapping out the drive and installing the Rockbox firmware. You can check out the full list on TechHive's website. If you have some mods of your own, please share them in the comments.