Prosebush is a collaborative fiction web site located at http://www.prosebush.com/
The site is not entirely unlike Everything2, in that anybody can sign up as a user and start contributing. The main difference is that the aim of the game is to create stories by stringing together the contributions of various people. Stories can be "forked" off in different directions, so multiple versions can co-exist. Stories are also categorised, so that users can concentrate on those genres that appeal to them.
At the time of writing, the amount of content is nowhere close to that contained in E2 (they recently celebrated their 1,000th entry), but the potential exists. One of the main problems which seems to bedevil the site is that story trees seem to become wide but not deep. That is, users tend to prefer to take the stories off in their own direction rather than drive it towards completion. There is also the tendency to contribute entries which do nothing to further the storyline, but which are intended to spark the imagination of the next contributor. While there is nothing wrong with this in theory, in practice it quickly becomes tedious to page through a series of entries which promise much but deliver nothing.
All in all, another interesting foray into the world of collaborative web sites, and one which serves a purpose distinct to that of Everything2. In fact, there is a great deal of content on E2 which make me want to yell: Take it over to Prosebush!. They are crying out for content, and would welcome a lot of the original fiction which is not always popular here on E2.