Understanding Solar System gravity

http://www.kidsgeo.com/geography-for-kids/0019-the-revolution-of-the-earth.php

http://www.physics4kids.com/files/motion_gravity.html

http://www.enchantedlearning.com/subjects/astronomy/planets/

http://www.enchantedlearning.com/subjects/astronomy/planets/earth/ 

http://www.kidsastronomy.com/solar_system.htm