Google has obtained newsgroup archives dating back to 1981.

check out <a href='http://www.google.com/googlegroups/archive_announce_20.html' > this page</a>, that includes the first posting to a newsgroup about AIDS (1982) as well as the first time there was a mention of Microsoft Windows (1983). And Tim Berners-Lee's announcement that he's working on a project called the World Wide Web (1991).