Critical Infrastructure Assurance Office
Formed in May 1998 by order of the President, CIAO is the national coordinating office for critical infrastructure assurance policy, working to defend key elements of the national infrastructure against physical or cyber attack.

Central Intelligence Agency
Links to speeches, publications, directorates, and the Center for the Study of Intelligence.

Defense Intelligence Agency
DIA provides information about its mission, publications, employment opportunities, and other public information.

DefenseLink
Office of the Secretary of Defense (Public Affairs) Includes press releases, contract announcements, briefing transcripts, etc.

National Intelligence Council
The public website of the NIC, the U.S. government's long-term strategic thinking body.  In recent years, beginning with Global Trends 2015, the NIC has been reaching out beyond the Intelligence Community to bring academics and private sector experts into its projects.

National Security Agency
Official NSA site, including the National Cryptologic Museum.

Navy Online
Includes links to the Navy News Service, Naval Air Systems Command, Naval Surface Warfare Center, and more.

North Atlantic Treaty Organization
NATO runs a web site with official releases, notes on Allied Command Europe and other major commands, and fact sheets.

Office of Homeland Security
Little needs to be said about this office.  Won't be around for much longer, though, as the new Department is organized.

Office of the National Counterintelligence Executive
Peculiar office created by Presidential Decision Directive to help make the public aware of a number of counterintelligence threats, including traditional espionage, industrial espionage, trade secret theft by insiders, that sort of thing.  Generates a lot of interesting awareness posters and other publications.

President's Commission on Critical Infrastructure Protection
Official site of the blue-ribbon commission formed to study the problem of critical infrastructure protection, whose October 1997 report, Critical Foundations, led to the formation of the CIAO.

United States Intelligence Community
Official site of the IC, comprised of the Defense Intelligence Agency, the National Security Agency, National Reconnaissance Office, National Imagery and Mapping Agency, Army Intelligence, Naval Intelligence, Marine Corps Intelligence, Air Force Intelligence, the Central Intelligence Agency, the State Department, the Energy Department, the Treasury Department, the Federal Bureau of Investigation, and the Coast Guard.