Infinite Chapters is a site that allows strangers to write a book together, piece by piece. You can read sections that previous contributors have written and then write something yourself. So far, there are only two chapters on the site. It's the start of a story about a guy named Jack who wakes up and realizes he is stranded on an uninhabitable island. I'm curious to see what this story will turn into after more people add on to it.
From the site: "On this website users create a story together. The story is made up of parts and each part has submissions by users. The top submission for a part is included in the story. Part one's top submission will be the first paragraph of the story and so forth for other parts."