History of Astronomy (Germany)
Created in January 1995 on behalf of the Working Group for the History of Astronomy in the Astronomische Gesellschaft, an international society for German-speaking astronomers. Since March 1998 this site has also been maintained on behalf of Commission 41 (History of Astronomy) of the International Astronomical Union.
NASA: National Aeronautics and Space Administration (U.S. Government)
This site includes news, mission information, images and video, and other information about NASA.
The Online Books Page (University of Pennsylvania)
This source provides links to approximately 70 free online books on astronomy topics. The site also offers searching and browsing by title and author.
Planetary Data System (PDS) (NASA)
The Planetary Data System (PDS) provides scientific data from NASA planetary missions, astronomical observations, and laboratory measurements.
Skyview: The Internet's Virtual Telescope (NASA)
Skyview is a user-driven image generator that presents customized images of any portion of the sky from a variety of surveys and in seven wavelengths.