[mark-t]

The only way to learn math is to do math, and you should learn to do math the same way you learn to program: solve problems that you find interesting.

Personally, I like to do contest problems. You can find tons and tons of them on John Scholes's website: http://www.kalva.demon.co.uk/ but they tend to be on the hard side. The AIME is possibly the easiest on there, and those are the sort of problems where the average high school only has one student every decade or so that can solve any.

There are contests for junior high students and less advanced high school students, too, but I can't find the problems online. There are books, though. You might want to look at the AMC 8, 10, and 12.

Or, you know, make some up. Think of a problem you've always been curious about, and try to solve it. There are forums online that can offer guidance. For example, I work on http://math2.org/mmb/ .