I just noticed that Debian has a single-CD distribution that uses Xfce as the window manager, Thunar as a file manager, and GDM as the desktop manager. It's a full-featured install, with GIMP and OpenOffice goodness standard. It seems a credible alternative to Xubuntu.
I installed it on a 128MB/466Hz machine as well as in the virtualized environment on my 1.7GHz laptop. In both cases I configured Xfce and GDM to use the minimal amount of eye candy, and in both cases the result seemed better than Xubuntu under similar circumstances. However, I will need some more testing to be sure.
Debian with Xfce/Thunar/GDM still eats a lot of RAM. On the 128MB/466MHz machine it's just barely tolerable. I really wish that Ubuntu and Debian would consider IceWM for their light-and-lean distributions as still nothing I have found beats it for performance and RAM use. I keep hoping to find something that's easier to install but as fast and usable (and maybe a bit more sexy) than IceWM/ROX-filer/XDM, but still no luck.