The 39 Clues Message Board have a lot of roleplays (RPs). This means that more than one person contribute in a story from their character's point of view (POV).
Some of the more notable RPs:
Name: Egypt RP
Founder: Vince/CommanderDetective7
Contributers: Red/RedPuppy47, Jason/FireDragon113, Dracia/BlackWolf360, Katherine/AmethystAlliance23 & Joe/FightingCobra225
Links: www.the39clues.com/messageboard/show/15673
www.the39clues.com/messageboard/show/24594
www.the39clues.com/messageboard/show/21311
Name: Into the Gauntlet: The Ultimate Challenge
Founder: Ashley/SteelBone2
Contributers: there are around 30 of them, including sponsors and reporters
Link: www.the39clues.com/messageboard/show/21296
Name: Immortals RP
Founder: ArtisticBeliever28
Contributers: N/A
Link: www.the39clues.com/messageboard/show/24939
Name: Le Collège des Cahill Unité et Excellence (The College of Cahill Unity and Excellency)
Founder: CommanderLucian12
Contributors: We have over 65 members, not all of them are active.