The wonder of slim distributions, Damn Small Linux, has been released in a version 1.2 and still is a pleasure to install on old, under-specced computers.
From the release notes:

Changes for DSL 1.2:
– New .dslrc to save local mirror and protocol.
– New GUI Mirror selector for .dslrc, Apps->Tools->Mirror Selector
– Enhanced mydsl boot time option to accept a directory
– Enhanced backup/restore now defaults to /home/dsl and
– with xfiletool.lst to specify files and dirs to exclude from backup
– Enhanced ndiswrapper,prism2, iwconfig GUI's for public access points
– Enhanced mydsl to prevent non-DSL user corruption
– Enhanced frugal and pendrive scripts to allow updates
– Updated monkey webserver to 0.9.1
– Updated busybox to 1.0
– New boot logo screen.
– New default theme, Tree_and_Moon

Download it here