Dennis Ritchie's home page (alas, now silent) has a great collection of papers and anecdotes about Unix, C and their development.

Groklaw.net and Pamela Jones did an extraordinarily amazing job of covering the SCO vs. IBM lawsuit.

The Unix Heritage Society collects, curates and maintains old Unix systems and information. They have a good mailing list.

Éric Lévénez has a great printable Unix family tree.

Kirk McKusick's web site has information about the BSD Daemon, the History of Unix at Berkeley and the CSRG Archive CD-ROM set.

George Coulouris' web site has details of his involvement in the history of Unix in the UK, including the em editor.