EtherPad – Real Time Collaborative Text Editing
http://etherpad.com/

EtherPad is the only web-based word processor that allows people to work together in really real-time. When multiple people edit the same document simultaneously, any changes are instantly reflected on everyone’s screen. The result is a new and productive way to collaborate on text documents, useful for meeting notes, drafting sessions, education, team programming, and more. This has been added to the tools section of Research Resources Subject Tracer™ Information Blog.