http://phet.colorado.edu/en/simulations/index
Clicking on the above link will take you to a page with many different simulations. They are all relatively small programs that can be downloaded to your computer. You do not have to have access to the computer to run them although you can choose to just use them from the web. Magnetism, electricity and math are a few of the subjects that are covered. There are over 80 different sims and you owe it to yourself to check them out. They are great for exploration or review of topics.
