URLs listed in this category:
An Atlas of The Universe
Contains maps of the universe zooming out from the nearest stars to the entire visible universe.
http://www.atlasoftheuniverse.com/
Heavens-Above
Provides all the information you need to observe satellites such as the International Space Station and the Space Shuttle, Iridium satellite flares, and other spaceflight and astronomical information.
http://www.heavens-above.com/
Astronomy.net
Articles, forums, clubs, vendors, manufacturers and other resources important to those interested in Astronomy.
http://www.astronomy.net/
Astronomy Today
Information and articles on astronomy, space and related topics. Also featuring a friendly forum and a monthly sky guide.
http://www.astronomytoday.com/
AbsoluteAstronomy.com
Facts and information about planets, moons, constellations, stars, galaxies, and Messier objects.
http://www.absoluteastronomy.com/
Astronomy Online
Astronomy Information and Resources.
http://astronomyonline.org/
Space.com
Space.com provides information on everything Space - satellites, stars, astronomy, the Sun, planets, NASA and more.
http://www.space.com/
BBC - Science & Nature - Amateur Astronomy
A guide to amateur astronomy from the BBC, including clubs and planetariums in the UK.
http://www.bbc.co.uk/science/space/myspace/