Exploring Planets in the Classroom:  Hands on Activities
http://www.spacegrant.hawaii.edu/class_acts/index.html
More than 25 hands-on science activities are provided in classroom-ready
pages for both teachers and students for exploring Earth, the planets,
geology, and space sciences. (Upper elementary and secondary)

Exploring the Planets
http://www.nasm.si.edu/ceps/etp/
Information about planets and space from the National Air and Space Museum.

Views of the Solar System
 http://www.solarviews.com/eng/homepage.htm
Discover the latest scientific information, or study the history of space
exploration, rocketry, early astronauts, space missions, and spacecraft
through a vast archive of photographs, scientific facts, text, graphics and
videos

Your Weight on Other Worlds
http://www.exploratorium.edu/ronh/weight/index.html
Ever wonder what you might weigh on Mars or The Moon? Here's your chance to
find out.

Skywatching Center
http://www.earthsky.com/Features/Skywatching/
Use the Skywatching Center tonight to go into your backyard, look up at the
wonders of the universe, and know what you're seeing.

Constellations and their Stars
http://www.astro.wisc.edu/~dolan/constellations/constellations.html
Find everything you need to know about constellations here.

Solar System Exploration
http://sse.jpl.nasa.gov/features/planets/planetsfeat.html
Explore the many wonders of our solar system.

Astronomy for Kids: The Planets
http://www.dustbunny.com/afk/planets/planets.htm
Take a journey through our solar system.  Also learn about famous astronauts
and space missions. (Elementary)

The Nine Planets: A Multimedia Tour of the Solar System
http://www.ex.ac.uk/Mirrors/nineplanets/
The Nine Planets is an overview of the history, mythology, and current
scientific knowledge of each of the planets and moons in our solar system.
Each page has text and images, some have sounds and movies, most provide
references to additional related information