Prentice Hall website for Astronomy: A Beginner’s Guide to the Universe 3rd ed.
Animations, illustrations and good practice questions. More excellent links.
http://www.space.com a site with lots of good space and astronomy information, activities, and other cool stuff.
http://www.heavens-above.com a website that helps one see and identify artificial satellites. Input your location and you get tables that tell where and when to look for satellites that are visible from your location.
North Carolina School of Science and Math (NCSSM)
Good physics and astro stuff including more excellent links.
NASA’s Spacelink Page, An Information System For Educators
A great astronomy site maintained by the publishers of Sky and Telescope magazine.
Astronomy magazine maintains a nice site.
Discovery Channel often has space and astronomy news.