SlimPup is a slim, fast, fully-equipped, and minimalistic Puppy Linux distro, heavily inspired by Crunchbang and Archbang.
New: Check out the Wikipedia article for more information.
Lightweight - runs using only 35-70mb of RAM and 600mhz of power
Fully-equipped - self-sufficient with apps of each category right out of the box
Small - only 425mb
Portable - save changes to your live CD/DVD and take your OS with you on the go