Initially not an expert at all, Thompson started compulsively researching the 9/11 terror attacks in order to come to some objectives conclusions around what happened and what lead up to the event. His timeline now includes some 1600+ events, which he compiled painstakingly, initially as a hobby, but eventually including feedback and refinements from people around the world until he has joined the California-based Center for Cooperative Research and has published what is now the most complete account of 9/11 yet. Journalists refer to his timeline as a sort of Terror Bible.
The Center encourages "grassroots participation and collaboration in the documentation of the public historical record using an open-content model." Kinda like Wikipedia, I guess, only with an extremely detailed focus.
Additionally, I found this objective of the Center particularly admirable, not to mention timely:
The Center for Cooperative Research calls on people to abandon the widely-held assumption that governments can be relied upon to competently monitor the activities of themselves or the entities with which they have close relations. A major goal of this website is to encourage people to play an active role in scrutinizing the activities of all individuals, groups and institutions that wield significant political and economic power. Our position is that the power of oversight should not rest with governments, but with civil society itself.(Mentioned in Esquire magazine, 12/04, p. 197)