conuly

Most of what I'm seeing online at the right level is either extended upward from the lower grades (http://www.coolmath.com, has very colorful explanations and straightforward practice problems), or downward from higher ed (http://www.sosmath.com, has multiple-choice self-tests and explanations). The self-tests might be good for identifying areas to focus on.

Drexel Math Forum (http://mathforum.org/students/high) has a ton of stuff, which may be worth exploring or may lead to a single useful resource. I don't know yet if that leads anywhere with an appropriately linear structure so you could work through it and learn sequentially. It's constantly maintained, but the overall structure is very Web 1.0, which is clunky.

This publisher produces the coolest Geometry textbook I've seen at any of the schools I've interviewed at. (Didn't get the job though.) If you click on the books, they have links to "condensed lessons" and practice problems, which might be enough? Except that I'm not sure how you check your answers. http://math.kendallhunt.com

Barron's EZ Calculus is generally recommended by other physics teachers as a great self-study tool for kids learning calculus on their own. It has a weird story, good explanations, and lots of sample problems. I don't know if the Calculus book is an exception, or if they have books like that on other levels as well.

As a precocious teenager, I thought the old UCSMP textbooks worked really great for teaching myself stuff. I'm not sure how well they would work for someone who wasn't me, though. (I think they also had some BASIC programming examples, which even back then we skipped.) My experience with the NYS Regents books five years ago was that they were much less good; I'm sure they've redone them again since then.

I have kind of a hoard of math textbooks in my basement right now, although that's probably not useful. And could probably also ask our actual math department if they have ideas. (I bet they have their own hoards of textbooks. Textbooks just kind of accumulate in offices and classrooms.)