I did a search on DistroWatch under the category of old computers and it come up with about 20 recommendations. The usual suspects came up; Puppy, DSL, Slitaz, Tiny-Core. The rest fell into two broad categories, the first being Ubuntu based distros using lightweight window managers. The second group were based on Slackware. I have a soft spot in my heart for Slackware. Wolvix was the first distro I could get my wireless card at the time (three years ago) working properly. Because of this Wolvix paved the way towards full time Linux usage breaking my Windows fix. I haven't looked back.
Absolute, AUSTRUMI, SaxenOS and Vector were the Slackware based distros that caught my eye. A quick review narrowed my interest to Absolute or Vector. I decided to install Vector on a 700mhz test machine with 512meg of RAM because they had just released their 6.0 Lite Version.
After the install I was greeted with a very usable system even on the 700mhz test rig. I was able to configure OpenSSH and VNC without any major issues. At boot, running JWM as the window managers, I was using only 50meg of RAM and CPU utilization was in single digits. I am very impressed with Vector so far!