A col­lab­o­ra­tive sto­ry­telling site that encour­ages users to write short bits of fic­tion. Oth­ers can react to those sto­ries with sequels or (the neat­est part I think) pre­quels. There is also the pos­si­bil­i­ty of post­ing chal­lenges, which are just that — chal­lenges to users to write some­thing accord­ing to some kind of theme or oth­er con­straints.