Had a look at the Alternate Reality Game (ARG) promoting the latest Matrix movie yet? It’s centred around the at first glance run-of-the-mill Metacortex site, perhaps continuing via their employee of the month’s personal website. At some point you’ll probably want to use an intro like Brian’s over at Ratchet Up – piecing together a puzzle-story like this requires collaboration. Down the Rabbit Hole provides a good overview.

Unfiction.com provides a general introduction to this kind of gaming, and Jane McGonigal’s DAC paper on immersive gaming is great reading too.