CK-12 is a non-profit with an impressive list of educational partners. It has resources in a ton of subjects, and just unveiled a bunch of neat physics interactives.
But what’s particularly impressive to me is the ability for teachers to set-up virtual classes, create assignments, and track individual student progress on the work. It has lot of other bells-and-whistles that I’ve just begun to explore, including the ability to leave virtual post-it notes on many of their resources.
I’m adding it to The Best Sites That Students Can Use Independently And Let Teachers Check On Progress.