Yup, I have been using this extensively. Paul's notes are something I forgot to mention-I referred to them almost daily, back when I was taking the equivalent of Calculus 1, and they're still very useful now that I'm taking differential equations.

Unfortunately, this doesn't quite work on OpenStax-I can't get LaTeX, all I can get is MathML, and that's not very easy to read. There's a way to navigate the math (using something called mathplayer), but it's quite inefficient as compared to LaTeX, specially as I go into higher math. The books are still very, very good, though.