Exploring the Planets
- http://www.nasm.si.edu/ceps/etp/
- Sponsored by the National Air and Space Museum, contains many interesting facts about the planets, pictures, comparisons and a section dedicated to spacecraft.
SkyScopes
- http://www.skyscopes.com/
- Information about planetary astronomy and space exploration and habitat. Online chat, message boards, and related links. Sells replicas and toys.
Solar System Dynamics
- http://ssd.jpl.nasa.gov/
- Provides detailed information related to known bodies in orbit around the Sun. Ephemerides, physical parameters, Earth close-approaches, observer tools.
Solar System Simulator
- http://space.jpl.nasa.gov/
- Online software that generates views of the bodies of our planetary system at any date from any artificial or natural point of observation.
The Nine Planets
- http://www.nineplanets.org/
- Overview, sections dedicated to each planet and the smaller bodies - with data, information and some pictures - glossary and appendices.
Windows to the Universe
- http://www.windows.ucar.edu/
- Aimed at portraying Earth and Space Sciences in a fun way. Includes information about space weather, global space physics and a real time movie of current solar activity.