http://www.engineeringinteract.org/interact.htm
http://www.thetech.org/exhibits/online/topics/12a.html
Design a Roller Coaster
http://www.learner.org/interactives/parkphysics/coaster/
http://www.funderstanding.com/coaster
Electricity
http://www.quia.com/pop/96319.html
http://www.quia.com/jg/639039.html
Electromagnets
http://www.harcourtschool.com/activity/electromagnets/