UK Government

• UK DirectGov
• CCTA's UK Government Information Service
• The Public Whip
• UK National Statistics
• Department of Health
• UK Transplant
• Environment Agency
• The Met.Office
• Ministry of Defence; the Royal Navy; the RAF
• The Foreign & Commonwealth Office
• The Security Service, MI5; recent document releases
• Contact details for MI5 and MI6 (SIS) - third-party site (amusing in its own right, as it carries copies of communications between a man who believes the security services are watching him, and those services)
• UK Parliament
• 10 Downing Street
• Official Documents from HMSO
• The Cabinet Office
• The Data Protection web site, and the Data Protection Act 1998
• Almost governmental: the Telephone Preference Service and Mailing Preference Service, to opt out of junk mail and phone calls.

US Government

• CIA; Office of the Director of Central Intelligence; The Intelligence Community
• FBI
• Intergovernmental Panel on Climate Change
• NASA; NASA Jet Propulsion Laboratory
• NSA
• Department of Justice; Drug Enforcement Agency
• The White House
• US Air Force
• Sandia National Laboratories

Other

• NATO
• King Hussein of Jordan