MIRA - Why do Stars Twinkle?
http://www.mira.org/fts0/stars/text/txt001c.htm
Monterey Institute for Research in Astronomy explains the cause of this mirage as refraction.

Multimedia Tour of the Sun
http://www.astro.uva.nl/demo/od95/
At this site you can take a tour to the Sun and learn about its development, structure, and influence.

Mysteries of Deep Space
http://www.pbs.org/deepspace/
At this site you can view an interactive time-line, classroom activities, ask the experts, trivia, and Hubble telescope news.

NASA Online Resources
http://image.gsfc.nasa.gov/poetry/
Collection of sources at NASA and affiliated organizations including online games, galleries, teaching material, and experiments.

NASA Spacelink
http://spacelink.nasa.gov/.index.html
Current NASA programs and educational materials. Articles on everything from living in space to the big bang theory.

NASA
http://www.nasa.gov/
The official site of NASA which is deeply committed to spreading the unique knowledge that flows from its aeronautics and space research.

Photo Gallery of Mars
http://nssdc.gsfc.nasa.gov/photo_gallery/photogallery-mars.html
This site has a photo gallery of Mars taken by orbiting and landed spacecraft.

Planetary Fact Sheets
http://nssdc.gsfc.nasa.gov/planetary/planetfact.html
National Space Science Data Center provides a useful collection of data on the planets, their orbitals, and atmospheres.

Shuttle Team Online
http://quest.arc.nasa.gov/shuttle/
Communicate with the space shuttle team and learn about their jobs. With a photo gallery, background info and educational resources.