The Mars Show (narrated by Patrick Stewart) and specific Mars links.
The Nine Planets Maintained by Bill Arnett. Great place to start!
Views of the Solar System Maintained by Calvin J. Hamilton. Includes every planet and satellite, plus asteroids and comets. Detailed and accurate. Highly recommended.
History of Space Exploration Maintained by Calvin J. Hamilton. Covers from Sputnik and Apollo to Mir and current missions. Wonderful!
Solar System in 3-D. Great 3D pics!
Tour the world's largest Solar System Model, in Peoria, Illinois, hosted by Bradley University Physics department and Lakeview Museum. Or tour it by bicycle! This interesting website also includes the following pages:
Solar System Browser. Maintained by the US Geological Survey.
The Basics of Spaceflight Learners' Workbook. A tutorial by Dave Doody and George Stephan (both of JPL) for middle school students and older.
Hubble Space Telescope
Jet Propulsion Lab (JPL)
Astronomical Image Index. 15,000 image links!