I have been looking into 'Modeling Instruction' as a way to teach students conservation of energy in a more conceptual way.  To this end, I would like to start with a simulation/applet that shows a spring launcher and the exchange of energy between elastic, kinetic, and thermal using pie and bar graphs.  The students would first develop their own pie/bar charts after observation of the simulation and then have them verified.  I've attached a better explanation of what I mean.