Warren Sack, Conversation Map v.2.0 (2000)

Using techniques from computational linguistics, social network analysis, and information visualization, the Conversation Map automatically summarizes and produces an interactive diagram of hundreds or thousands of email messages sent to online public discussions. The diagram includes three parts: a social network visualizing who is exchanging messages with whom; a list of discussion themes, a menu of topics being discussed; and, a semantic network that shows which topics are discussed in similar terms; or, in other words, the synonyms or metaphors that are emerging from the discussion.

http://hybrid.ucsc.edu/ConversationMap/