Most of finance is built from a few standard formulas and strategies. For example, investments tend to grow like compound interest and pay out like annuities; and you judge them by estimating future profits and then calculating present values or equivalent rates of return.
So here are the basic building blocks, from the easy to the ugly.
This article uses interactive graphs to demonstrate some key financial concepts; just using the graphs will be enough for most people. But if you’re nuts about numbers, you can also see where the various formulas come from.
Editor’s Note: This is a good for introductory material; you may also find the parent site—moneychimp—of interest.