McDonald's has released an alternate reality game tied to its support of the Beijing Olympics called The Lost Ring

"The Lost Ring" is a type of game known as an Alternate Reality Game (ARG), which does not require any software installation and can be launched as a "browser game" on a Web browser. Unlike adventure games that focus on puzzle-solving, the clues to unravel the mysteries in this game are hidden both online and in the real world. Blogs, interconnected web pages, telephones, and radio broadcasts—all these elements are crucial to solving the puzzles. It's difficult for one person alone to successfully complete the challenge; it becomes easier when players who use the web share information together.