Desmos
“Graph functions, plot data, evaluate equations, explore transformations, and much more – for free!”
nanoHub
“Our site hosts a rapidly growing collection of simulation tools for nanoscale phenomena that run in the cloud and are accessible through a web browser. In addition to simulations, nanoHUB provides online presentations, cutting-edge nanoHUB-U short courses, animations, teaching materials, and more.”
Oyez
“Oyez (pronounced oh-yay)….is a multimedia archive devoted to making the Supreme Court of the United States accessible to everyone. It is a complete and authoritative source for all of the Court’s audio since the installation of a recording system in October 1955.”
PhET
“Founded in 2002 by Nobel Laureate Carl Wieman, the PhET Interactive Simulations project at the University of Colorado Boulder creates free interactive math and science simulations.”
Society Pages
“The Society Pages (TSP) is an open-access social science project headquartered in the Department of Sociology at the University of Minnesota and supported by individual donors. TSP consists of in-house ‘TSP HQ’ articles, blogs, and podcasts; our ‘Community Pages’; and content produced by our partners.”
STEM Sheets
“Free Customizable Flashcards, Worksheets, and Diagrams”…in Science, Technology, Engineering, and Math.
WolframAlpha
“WolframAlpha is a computational knowledge engine for computing answers and providing knowledge….it generates output by doing computations from its own internal knowledge base, instead of searching the web and returning links.”