U.S. Federal Agencies:
Bureau of Alcohol, Tobacco and Firearms
Bureau of Diplomatic Security
Bureau of Indian Affairs Law Enforcement Services
Bureau of Justice Statistics
Central Intelligence Agency
Coast Guard
Coast Guard Gulf Regional Fisheries Training Center
Customs Service
Defense Security Service
Department of State
Department of Veterans Affairs Police - Indianapolis
Drug Enforcement Administration
Federal Bureau of Investigation
Federal Bureau of Investigation, Norfolk VA
Federal Bureau Of Prisons
Federal Law Enforcement Training Center
Federal Protective Service Police
Federal Protective Service Police Fort Worth, TX
Fish & Wildlife
Health & Human Services, Office of Inspector General
Immigration and Naturalization Service
Internal Revenue Service Criminal Investigation Division
Justice Department
National Fish & Wildlife Forensics Lab
National Institutes of Health Police
National Institute of Justice (NIJ)
National Law Enforcement & Corrections Technology Center
National Park Service
National Security Agency
Office of the Assistant Inspector General for Investigations
Postal Inspection Service
Protective Services
Secret Service
Trade Commission:
Treasury Department
United States Air Force Office of Special Investigations
U.S. Attorney General Janet Reno
United States Border Patrol
U.S. Coast Guard, Office of Law Enforcement
U.S. Dept. of Veterans Affairs Office of Security and Law Enforcement
U.S. Office of Export Enforcement
U.S. EPA Criminal Investigation Division (CID)
U.S. Federal Protective Service Police, Miami
United States Intelligence Community
United States Marshals Service
United States Park Police
United States Parole Commission
U.S. Tennessee Valley Authority Police

If you don't see it above, try the Directory of Federal Agencies