PhET is a free website, with simulations built in Java, HTML 5 & Flash. The simulations built in Java didn't work on our chromebooks because they have to be downloaded, though we were able to get them to work on our laptops by control clicking to get around the security warnings. Our students chose the simulations built in HTML 5 & Flash, which happily the PhET creators indicate on each simulation.
After a quick introduction, Mrs. Wilson's student took off exploring with great enthusiasm! The room erupted with chatter as students clustered together to share their discoveries. It was a fabulous day of learning and PhET is officially my favorite digital science and math tool for students!