Although it's neither Debian nor Ubuntu, I have to give props to the new mini distro on thestreet, Slitaz. I tested out the cooking version (looking for ideas on software for my ancient computer project) this afternoon and took some screenshots.
It uses OpenBox + LXPanel and PCMan. It even manages to fit FF3 RC1 into the svelt 25MB download. I encourage you to take a look at it.
It hs its own package manager called tazpkg (the packages are taz files). It supports basic lists off of the mirror and apt-get style installation with dependency resolution. Extra packages of interest include Pidgin 2.4 and Abiword 2.6.3, which I gave glowing marks in my previous review.