Neal Stephenson, author of Snow Crash, is using a wiki for participatory learning for his new book Quicksilver:

The Metaweb is a collaborative structure for learning. In our first phase, we are annotating the ideas and historical period explored in Neal Stephenson's novel Quicksilver, seeding the Metaweb with an initial base of information. We are currently working on 108 articles, and hope you will expand and relate these and many other entries...

[via Joi via BoingBoing via Jeremy]