Great suggestions as always, just adding xubuntu
Debian + the nice (graphical) app tools (yeah, I know, apt, but for new converts it's nice to have graphics) + XFCE4 = good.
Only played with this in VMWare but I was very impressed. Nice quick slick distro. To get the best from it you do need to stick with package selection or you quickly end up adding bloat.
I'd also second DSL and add Slax to the list... both are good solid distros and ther are a few variations of Slax so you might find a good match.
If you want to have a real laugh boot DSL from CD on a reasonable machine with 512Mb of ram or more.. ues the toram option on boot and just have a play.... quick is not the word! (also works in VMWare that way