a great resource for free e-textbook and curricular resources, has just announced that there are now over 100,000 teacher-created digital textbooks available online on their site. These new "Flexbooks" were created by the 30,000 schools that are using CK-12's free digital resources.
They also have some great physics simulations and other resources available, as well as new elementary math resources and PLIX (Play, Learning, Interact, eXplore) which provides an interactive and immersive experience where students learn by doing, allowing them to use critical thinking and creativity.
Math
Grade 1–5 Arithmetic Measurement Algebra Geometry Probability Statistics Trigonometry Analysis Calculus
Science
Earth Science Life Science Physical Science Biology Chemistry Physics
English
Writing Spelling
More
Engineering Technology Astronomy History
Created By Dhruv Patel And Team