Science teachers can go on OpenSciEd and sign up for a free account. Once they have it, they can download curriculum units that include videos, simulations, and lessons which they can then share with their students. While not all of the activities work for at home science learning, many do.
Amplify has assembled a resource bank for students K-8 of free educational materials. Their site includes novel studies for elementary and middle school students, an adaptive reading program, read aloud lessons, and science lesson videos for elementary and middle school students.