NASA
Astronomy Picture of the Day - Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer (100 visits)
http://antwrp.gsfc.nasa.gov/apod/
Jet Propulsion Laboratory - (85 visits)
http://www.jpl.nasa.gov/
Missions - (119 visits)
http://www.nasa.gov/missions/highlights/index.html
NASA - (80 visits)
http://www.nasa.gov/home/index.html