Recommended materials sorted by type and by grade level (including college and instructor level).
http://www.astronomyinspanish.org/
Introductory course taught at the University of Oregon. Includes course materials and many links to supplementary resources.
http://zebu.uoregon.edu/astr121.html
An interdisciplinary course on cultural astronomy. The course has a goal of imparting an understanding of basic astronomical phenomena and an appreciation of their cultural significance throughout the world.
http://www.math.nus.edu.sg/aslaksen/teaching/heavenly.shtml
PBS companion site explores the secrets of the universe with an interactive timeline, classroom activities, a trivia challenge, and questions and answers with experts.
http://www.pbs.org/deepspace/
Virtual museum and planetarium. Learn about cosmic evolution, from Big Bang to Humans.
http://www.cosmicvoyage.org/
Department offers astronomy degree programs for undergraduate and graduate studies with research opportunities at Steward Observatory.
http://www.as.arizona.edu/department/
Learn about Solar System, space exploration and constellations.
http://starryskies.com/index.html
An affiliate of the National Science Teachers Association.
http://solar.physics.montana.edu/aae/