Are there alternate OSes for the click-wheel iPods?
An alternate OS is Rockbox. It is a free firmware replacement that works on many music players. Rockbox supports:


  iPod 1g through 5.5g, iPod Mini, iPod Nano 1g and iPod Nano 2g


One downside to Rockbox is that you have to make your iPod a Windows formatted partition on a Windows computer.

There are many different themes for Rockbox. Here's an example of just one: