Simple Machines

Learn more about 1st class, 2nd class, and 3rd class levers. There are 
simple animated drawings of levers in action.
http://www.enchantedlearning.com/physics/machines/Levers.shtml

This page has levers and other simple machines.
http://www.mos.org/sln/Leonardo/InventorsToolbox.html

This site lets you explore simple machines with a variety of games and activities.
http://edheads.org/activities/simple-machines/

Learn more about the different types of simple machines.
http://www.smartown.com/sp2000/machines2000/main.htm

Another interactive site to investigate the 6 simple machines.
http://www.mikids.com/Smachines.htm