Chromium is pretty good. I believe it's on the MDK CDs or you can find it on rpmfind.net.
I did see a linux port of Raptor but the link to download it doesn't seem to be working.
I ran every version of MDK since 6.0 on a P133 with 48MB RAM.
It worked just fine for me and I was using KDE & Gnome. It was a bit slow but fine for email and websurfing. I was also running it as my "do all" server at the same time.