If you are looking for free math resources, I found a website that offers peer-reviewed math ebooks for college and AP Courses. This website is OpenStax which is based in Rice University and supported by several foundations. Below are the links to the math ebooks.
- Algebra and Trigonometry
- Calculus I
- Calculus II
- Calculus III
Aside from the math ebooks on Science, Social Science, Humanities, and AP Courses are available on the website.
For more free resources, you can visit Math and Multimedia’s All for Free page.