colorforth is an operating system written by Chuck Moore which runs on some x86 PCs. There are various ports so that you can run it under x86 GNU/Linux, Windows, bochs, and some PCs that don't run the original version.
Links to information about colorforth
colorforth channel IRC chatroom dedicated to colorforth.
colorforth mailing list: http://www.strangegizmo.com/forth/ColorForth/
colorforth programs and some ports: http://www.dnd.utwente.nl/~tim/colorforth/
how to run colorforth under bochs
If you have trouble getting colorforth to run on your computer, drop by the colorforth channel (off topic please.)
herkforth (a colorforth-like system for PPC)