http://www.stitz-zeager.com

For calc 1 - 3:

http://www.apexcalculus.com

I did find one really good intermediate algebra book but can’t find the website.

https://github.com/fabiohenriquecn/wisconsin-calculus

edit: I guess as of this semester these are no longer being used in classes, they've moved to the online homework / $300 textbook model.

https://www.people.vcu.edu/~rhammack/BookOfProof/