Simulations are very powerful tools for students to transform knowledge into action. I recently came across a great site designed by the University of Colorado called PhET.
Here is the link to a database of all of the free simulations available for all to use and categorized by subject, topic, grade level, and language.
Worried about accessibility? This tool is perfect for learning environments designed to meet the needs of all students! The following link provides a list of accessibility features and simulations containing these features.