Fun, interactive, research-based simulations of physical phenomena from the PhET™ project at the University of Colorado. Contains over 110 million simulations.
[CC BY 3.0 US or license, see Licensing page; The source code and executable versions of all simulations by PhET Interactive Simulations, University of Colorado are licensed under a Creative Commons GNU General Public License]
MyOpenMath runs on the open source, IMathAS platform, providing free hosted use of this platform in support of free, open textbooks like the ones listed on OpenTextBookStore.com. While students may use the resources for self-study, fees may apply for instructor-led courses.