Normally I don't get too excited about Mac hype about anything, but this time I'm jealous. Hydra is a text editor which supports editing of a document by more than one user at the same time. It's available as freeware, but only runs on the Mac.

What a fun tool this would be in the writing classroom. Note in the screenshot how each user's work is color-coded. And read about Robert Kaye's experience with Hydra during the ETech 2003 conference.