The Abandoned Project is something I came up with a few year ago. I've always enjoyed looking at pictures of old, abandoned buildings. What I've done is tried to capture all the details of different settings, but in text form.
The premise is simple: Fill up an imaginary building with detailed descriptions of rooms. Other people can then wander around these buildings and read the descriptions. Perhaps one person will try to duplicate an old hotel they stayed in during their last vacation ("I'm pretty sure the place was haunted. I heard people talking, but there was no one there!"). Another person might come up with a murder mystery for guests to solve ("The only occupant in the room was a skeleton, sitting in a corner with a meat cleaver in its skull. This isn't what you normally find in a janitor's closet.."). The possibilities are endless.
Eventually, the Abandoned Project will be split into two types: Abandoned Building, in which the story is room/grid based, and Abandoned Story, in which the layout is more story-centric. At the moment, Abandoned Building is the only option completed.
To view a general example of this type of subsite, click here. A demo subsite that you can test drive is located here. I also have one that I'm working on my own, called 1425 Forgotten Lane. If you'd like to create one of your own, then sign up!