A hode-podge of documents I've recently found, mostly on government sites
College of Policing [UK]
Undercover Policing: Authorized Professional Practice (draft version for public comment) [PDF] [memhole2 mirror]
Department of Justice, Criminal Division
Electronic Surveillance Manual, June 2005 [PDF] [memhole2 mirror]
Electronic Surveillance Issues, November 2005 [PDF] [memhole2 mirror]
Department of Justice, Office of Information Policy
Archive of "FOIA Update" newsletter, 1979-1999 [webpage]
CIA
The CIA responded to my FOIA request for recruitment posters targeting women, here's one example: pic.twitter.com/j7LLYtvzS2
— Runa A. Sandvik (@runasand) June 30, 2016
Department of Defense Inspector General
Review of the Policies for Prepublication Review of DoD Classified or Sensitive Information to Ensure No DoD Sensitive or Classified Information is Released to the Media [PDF] [memhole2 mirror]
FBI
Biometric Center of Excellence [website]
FBI Biometric Specifications [website]
Security Intelligence Review Committee [Canada]
Proceedings of the Intelligence Review Agencies Conference, 1999. Attendees included Inspector General officials from CIA, NSA, DIA, NRO, and Defense Dept, as well as high-ranking intelligence-oversight officials from UK, Canada, Australia, Belgium, etc. [PDF] [memhole2 mirror].
US Army Chemical Corps
Video: Vulnerability to Covert Attack [1959]
Red Cross Institute for Crippled and Disabled Men
Reconstructing the Crippled Soldier [circa 1918]
Other
Welcome to Fort George G. Meade: “The Nation’s Center for Information, Intelligence and Cyber Operations” [PDF] [memhole2 mirror]
The complete run of the original YIPL/TAP newsletter (1971-1984), the first publication devoted to phone phreaking (i.e., hacking the phone system). It also covered related topics, like hacking credit cards, the postal system, birth certificates, physical locks, etc. The vast majority of the info is hopelessly dated, but it's a fascinating historical document. [Internet Archive]