Blossoms- Math and science video lessons for high school students
Illustrative Mathematics- Comprehensive math curriculum, including student tasks, lesson plans and a format for engaging mathematical discussion.\
NCTM Illuminations- Interactive lessons searchable by standard
Math Planet- Math courses in pre-algebra, algebra I, alg II, and geometry. Also has practice tests for SAT and ACT.
Math is Power 4U - math videos
Open Algebra- open problems, videos and interactives. All content is CC-BY-NC-SA
PHET Interactive Simulations - Interactive simulations from the University of Colorado Boulder, licensed under CC-BY