CG Explorer Guide: AlternateRealityGamesARG, Main.

Alternate Reality Games (ARG)

Alternate Reality Games (ARGs), or Cross-Media Entertainment (CME), are where the game breaks out of being a dedicated application on your PC, and instead becomes a part of the world in which you live.

Since 2001, they have been breaking exciting new ground in online gaming, appearing to redefine some of the accepted rules of game development:

virtual worlds where all the players are constantly altering the world by their actions
characters that manifest in the real world, yet every nuance of interaction feeds back into the game
deep stories that effortlessly suck-in the players and hold them rapt
thousands of players at a time collaborating intensively, with no griefing

From: Welcome to the ARG SIG

Resources on Alternate Reality Games (ARG)

IGDA ARG SIG Alternate Reality Games Special Interest Group