(note: This site has no official affiliation with any other site)
Chris Brown's SCO.NeverHad.Info or SCO.HasNo.Biz or SCO.IsABad.Org (and others)
Al Petrofsky's SCOfacts
Documents and links at FinchHaven
WeLoveTheSCOInformationMinister
Scott McKellar's SCO and Linux FAQ
Harlan Wilkerson's historical notes (now defunct)
Dennis Ritchie's page containing USL v. BSDi documents
Eric Levenez' Unix Timeline