Qwikstory is a social network site that lets users create stories 1000 characters at a time.
"The site provides great opportunity for use in educational environments in which classrooms can collaboratively and virtually work on concepts like writing. McFadden adds the site is also a good opportunity for non-English speakers to practice their reading and writing skills in a more connected manner.
...The story threads can also be made private and only accessible if invited by the creator."