Solar System Simulator
Select a planet and satellite as seen from anywhere in the solar system and get detailed surface maps.
http://space.jpl.nasa.gov/

Star Map
Mt. Wilson Observatory brings you a detailed star map for your current location. Just enter the date, time, and location to receive a map of the sky. Other features allow you to customize your map.
http://www.mtwilson.edu/Services/StarMap/

Skyglobe Software
Download this shareware package and view the sky with loads of options.
http://www.physics.csulb.edu/100lonline/skyglobe/skyglobe.html

Amazing Space
Go galactic by building your own Milky Way. Learn about starlight, find space trading cards, and take the astronaut challenge.
http://amazing-space.stsci.edu/