National Aeronautics and Space Administration (NASA) is the major space-related agency in the U.S. Government, and its presence on the web is voluminous. The search engine offered on the main page searches all of NASA's many web sites.
To connect to the websites of any of NASA's subsidiary labs and centers, such as the Jet Propulsion Lab and Houston's Johnson Space Center, look under "About NASA," then "NASA Locations."
This Office in the Federal Aviation Administration (FAA) has a science-fiction feel to its title, but is full of down-to-earth information for anyone considering a commercial space launch or just curious about it.
The Naval Observatory is one of the oldest scientific agencies in the country, an important authority on time-keeping and astronomical measurements connected with navigation. Data products related to the following topics can be found on their website:
The Astrogeology Science Center, run by the Geological Survey of the Department of the Interior, supports efforts to explore, map, and understand our solar system. Their website includes databases, general and technical information, photo galleries, etc., concerned with our planetary neighbors.
One of their projects is Map-A-Planet, an interactive site which can produce customized maps of the surfaces ...