I found a suite of physics simulations (one of the simulations is a chemistry simulation) at the University of Colorado at Boulder. These are Java-based simulations so if you want to view them you will need to have the proper Java Runtime Environment installed on your system. Standard desktop systems at Missouri S&T should already have it and if you don’t, you should be prompted to install the right JRE when you try to view one of the simulations.
By themselves, the simulations can be difficult to work with, but if used within the context of a class where the instructor can provide the guidance needed to interact with the simulation, I could see where these could be very useful to illustrate particularly difficult concepts in physics and chemistry. For instance, the Quantum Tunneling and Wave Packet simulator definitely requires some guidance from an instructor who can explain the concept of quantum tunneling and what the various factors involved the process are (one of the options available allows you to configure the energy of the wave in the simulation, which has a significant impact on the probability that a wave will have sufficient energy to be measurable on both sides of the energy barrier–there is always some probability to find the wave on both sides of the barrier, but higher wave energy and lower barrier energy means the probability increases).
Anyway, I encourage instructors who teach physics or chemistry to at least take a look at these simulations. Other simulations include projectile motion (by firing various objects out of a cannon), http://phet.colorado.edu/new/simulations/sims.php?sim=Balloons_and_Static_Electricity, conservation of energy (by creating your own skate park), and salts & solubility.