Beginning with the break after season 2, Lost fans have had the chance to "play" Lost while gaining clues to the mythology.
While the games are entertaining and give us Lost fans something to do between seasons, it's important to remember that what happens in the ARGs is not necessarily cannon, meaning what happens during the games will not necessarily fit into the plot and real mythology of the show.
Lost's Alternate Reality Games:The Lost Experience
Game took place: Season 2 to 3 hiatus, May 2006 - October 2006
Game details: Rachel Blake, an ex-employee of the Hanso Foundation, set out to expose the foundation by leaving clues for gamers to put together.
More information: The Lost Experience
Game took place: Season 3 to 4 hiatus, January 2008 - February 2008
Game details: Sam Thomas searches for his girlfriend, Sonya, who was a flight attendant on Oceanic Flight 815. Gamers find clues to help Sam in his search.
More information: Find 815
Dharma Wants You and Dharma Special Access
Game took place: Season 4 to 5 hiatus, May 2008 - January 2009
Game details: Octagon Global Recruiting is recruiting volunteers for the Dharma Initiative. Gamers take tests to see if they will be recruited. This then turned into Dharma Special Acess, with emails and videos from co-executive producers Damon Lindelof and Carlton Cuse.
More information: DSA and Dharma Wants You