I recently discovered the wonderful MathJax. MathJax is a JavaScript library that displays mathematical formulas in web pages. It's very easy to set up and it renders beautiful mathematics.

For example:

Suppose \( U \) is an open subset of the complex plane \( \mathbb{C} \), \( f : U \mathbb{C} \) a holomorphic function, and the closed disk \( D = \{z : |z z_0| r\} \) is completely contained in \( U \). Let \( \gamma \) be the circle forming the boundary of \( D \). Then for every a in the interior of \( D \):

$$ f(a) = \frac{1}{2 \pi i} \oint_{\gamma}{ \frac{f(z)}{z-a} dz} $$

where the contour integral is taken counter-clockwise.

That is, of course, Cauchy's integral formula.