Here are the links to a few of my favorite FREE resources for STEM:
1. Phet – Great Simulations Developed by the University of Colorado team. All free, can be downloaded anywhere.
2.CWSEI – Carl Weiman Science Educational Initiative – great resources for K-16 STEM educators. In case you do not know, Carl is a Nobel Prize winner in physics. He was the main figure behind Phet as well.
3. Compadre – This one for physics and astronomy, but at any level.
Physics and Astronomy Education Communities
4. AAPT – American Association of Physics Teachers