I got an old laptop donated a while back, Pentium 133 with 24 MB RAM, no CDROM, no USB. I wanted to provide it for someone else as a basic internet surfing and office writing station and faced the problem what system would be suitable for that.
I tried some old flavours of Debian, but wasn't really happy. Then I found that there's a dsitribution called DeLi Linux that seemed to be just perfect. What they're doing is providing an intelligent mix of current and old software (yeah, xorg really runs on a P133). They have installation floppies for network install (well, it was nontrivial to find three floppies in my room). It's all a bit like doing Linux by foot, they're missing a real package management (they have one, but no auto-dependencies) and things like that, but that didn't really hurt.
In the end I had an IceWM-Desktop, together with Konqueror-Embedded, alternatively you can use Firefox 1.5 (they backport security fixes) linked against plain X-libs. Texts can be written with AbiWord, linked against gtk1.
It's a nice solution, if you once need some system for a machine where xubuntu is far too bloated, you might want to try out DeLi Linux. According to their webpage, it runs on a 486 with 16 MB.