https://phet.colorado.edu/en/simulations/category/math interactive simulations for math.
https://illuminations.nctm.org/Search.aspx?view=search&type=ls&gr=9-12 quality standards-based resources for teaching and learning mathematics, including interactive tools for students and instructional support for teachers.
https://gm.greatminds.org/en-us/knowledgeonthego when schools are closed we’re providing FREE daily instructional video lessons for math (Grades K–12).
https://ed.ted.com/lessons?student_level=3&direction=desc&sort=featured-position Provides access to thousands of lessons and resources. You can filter results by student level and subject.
https://www.canfigureit.com/ The CanFigureIt Geometry team’s mission is to nurture students’ deductive reasoning skills through independent, highly interactive exploratory learning.
http://www.ams.org/home/covid-19 American Mathematical Society Resources & Updates.