A Boston Globe article today, FBI Gives a Glimpse of its Most Secret Layer, discusses a special set of files kept in a separate location by the FBI that are its most secret (or most embarrassing). Pursuant to an FOIA request, the FBI released hundreds of pages of memoranda describing these secret files and outlining why certain information was deemed so sensitive that it had to be stored in this top-secret location.
The Globe piece does not provide the actual documents, but anyone interested can see all 476 pages of them at GovernmentAttic.org.