there is a Rebol Guide here:
Here are other 2 company that works with Rebol:
Do you know RED? It’s similar to Rebol, but open-source: http://www.red-lang.org
One liner of the week:
reformat: does [write clipboard:// remove head remove back tail entab mold load read clipboard://]
Copying rebol codes from a web site, tab indents are lost sometimes. This function will re-indent them correctly then you can simply paste.