Reuters
We were recently reminded of the wiki, called Intellipedia, after the website MuckRock published an entry for the fictional Key West "Conch Republic" earlier this month, which it obtained through a Freedom of Information Act request.
The system has been in use since late 2005, when the CIA piloted the effort. Since then, all 16 US intelligence agencies have come onboard to view and edit collaborative wikis, which are actually three different versions: Top secret, secret, and sensitive but unclassified.
You need valid credentials in order to access the system, which means it's off limits to the general public. But there have been plenty of FOIA requests to various agencies for entries over the years.
Here's what the system looks like.