[corey]

Have you mastered algebra and trig? If not, do it. Khan Academy is great for this. Watch the videos and do lots and lots of problems. In learning math, there is no substitute for working through lots of problems.

After this, I suggest learning some discrete math and proof techniques. The book How To Prove It is great. It will teach you logic, set theory, how to write proofs, and how to invent proofs. Learning this first will help you actually understand calculus when you study it next.

For calculus, MIT's OCW course is really good. Pick up a standard book like Stewart, do a lot of problems, and try to understand the proofs of all the theorems. Or if you'd really like a challenge and some more theory, pick up Spivak's book.