ALT-J, Volume 17, Issue 1 March 2009, 33-47. This case study describes the use of a synchronous communication application (MSN Messenger) in a large academic computing environment. (peer support c.f. Twitter)
Tweetree puts your Twitter stream in a tree so you can see the posts people are replying to in context. It also pulls in lots of external content like twitpic photos, youtube videos and more, so that you can see them in the stream without having to click through links.