MoonEdit is a collaborative editing tool. The examples shown online make it appear more like a chat application, but if you are doing any sort of collaborative writing it could be an interesting piece of software. An article in Wired gave a better example… in it they had several people attending the same conference and writing commentary about it at the same time. One was capturing raw content as the speaker was speaking, another was fixing spelling and grammar problems in what had just been written, and the third was posting editorial commentary. The first user was then able to capture without concern for spelling or formatting, etc.