The March 6th, 2003 edition of the New York Times included an article by Charles Herold on Alternate Reality Gaming that features the history of the genre presented very comprehensively, along with links to Cloudmakers, Unfiction, DeadDrop and ARGN.
The article traces the history of ARGs and mentions The Beast, Lockjaw, Uncap the Ride, Alias, and Push NV, among others.