Here are some of the best websites for space pictures:

The Jet Propulsion Laboratory (JPL), headquarters for NASA's robotic space program. You'll see great pictures from missions to Mars, Venus, Jupiter, Saturn and other planets.

The National Air and Space Museum, for pictures of the Apollo program that landed humans on the moon for the first time in history.

The Johnson Space Center, space shuttle headquarters.

The Space Telescope Science Institute, headquarters of the Hubble Space Telescope, for fabulous pictures of galaxies and other objects beyond the planets of our solar system.
-- Tom McDonough