An amazing look at iPod nano running iPodLinux from Joe Barr, a hard-core iPod- and Linux-fan:
I recently received an iPod Nano as a gift. My Nano is amazingly small, contains a gigabyte of storage, and sounds very good through its ear buds. It didn't take long for me to learn that folks have been putting Linux on iPods for a couple of years now, courtesy of the iPodLinux Project. Granted, the software for the Nano and most fourth- and fifth-generation versions of the iPod is experimental ...
Read more, it's a very well-written introduction to iPodlinux installation, with useful hints.