You can install the netbook packages over a standard 32-bit ubuntu installation. There are a couple of pages on the wiki for how to do that.

If you really want to stretch your brain install one of the BSD's and use that as your desktop for a while.

If you load up FreeBSD or OpenBSD and work through the documentation and stick with it for a couple of months you will be a better system administrator and a better developer because you will have been exposed to some of the different ways of solving the problems of building an effective operating system.