duviz.py is a simple UNIX command line utility written in Python to visualize disk space usage. See it in action here:
I started writing it a couple of years ago (2009 according to the git commit log), but I just recently decided to make it more public. As a happy git user, the natural choice was to put it on github (github.com/soxofaan/duviz) and I also spend some time to set up "Github Pages" for it to give it a more funky home page: soxofaan.github.com/duviz.
You might find it useful. Unless you work on Windows, in which case it's probably a piece of non-working codez.