Check out the ICS main page at http://www.ics-hub.org/
The goal behind the Immersion Music Method is the "20 Song Game," where your Lodge splits up and you all try to compose 20 brand new songs within a 12 hour block. You are to use absolutely no previously written music, and when the clock strikes the 12 hour mark, you have to put down whatever you are doing and call it a day. At the end of the day, all participating members of your Lodge get together and play for each other what came from their Day Session. There are many ways to play the 20 Song Game, but the afore mentioned method is the most common.
The Immersion Music Method was created by Nicholas Dobson and Michael Mellander, active members of Origin Lodge, Oakland CA. Since IMM's creation in 2001, ICS Lodges have sprouted up across the world, and a book has been published detailing the methods and philosophy behind IMM. The Frustrated Songwriter's Handbook can be purchased here.
This site is currently under construction. More info on members, as well as audio files of sessions will be posted soon.