Example using math in a webapge

I've wanted to include math with webpages for a long time. Wouldn't it be great if you could include an equation on a webpage, and have it rendered like in LaTeX?

It looks like MathJax does this.

\[ \cos \theta = \frac{1}{2} e^{j \theta} + \frac{1}{2} e^{-j \theta} \]

I am not affiliated with the mathjax project in any way.

-Michael Weeks, October 8, 2011
Updated May 2017 to reflect the MathJax hosting changes