Do you remember the good old gamebooks?
Well, long time ago, I started a project of this kind. I wanted to make something in-between a classical gamebook and a wiki, where everyone could extend and add arcs to the story. However, due to the usual indie hurdles (nobody gives a shit, lack of time/motivation, ...) it quickly came to a halt. I stumbled over it on my hard drive recently. Before it gets scraped forever, I thought it was maybe worth showing/giving it, in case anyone would like to make something out of it.
I uploaded it here: http://www.istory.hol.es
...sorry if it's a bit half-assed, but many things got broken during the "restoration" and I didn't want to spend too much time fixing it. Anyway, you get the picture. Who knows, perhaps you can even enjoy it a little bit. ;) I still think the concept is actually quite ok, to have some kind of nearly infinite book/game everyone can improve. However, I'm not really in a position right now to go on with it. ...and ideally, I think it would be great to add some "multiplayer" aspect to it, even if I have no idea at all what it actually would be. Feel free to post if you have some inspiring ideas.
If any person is interested in the idea/code/graphics, whatever, you can gladly have it all. ...or perhaps I should just put everything in a public repository, dunno.