MedlinePlus (National Library of Medicine) - This site includes information about drugs and supplements, diseases and conditions, and medical procedures.

National Aeronautics and Space Administration (NASA) - Information and links related to the space program, the international space station, astrological phenomena, and aerospace technology.

National Hurricane Center/Tropical Prediction Center (National Weather Service, Florida International University) - Gives information about current and previous hurricanes/cyclones, current weather conditions, and the tropical outlook.  Includes current satellite images.  

National Technical Information Service (NTIS) - Provides access to a database of approximately 3 million government-funded reports of scientific, technical, engineering, and business related information.  Some are available in full-text online, others can be ordered from NTIS.

Occupational Safety and Health Administration (OSHA) - This site provides information about the laws, regulations, and standards enforced by OSHA.  It also has information about state occupational safety and health plans, and general information about safety and health in the workplace. 

Science.gov - Science.gov is a search engine for government science information and research results. Currently in its fifth generation, Science.gov allows searching of more than 200 million pages with just one query, and is a gateway to over 1,950+ scientific web sites.