MathJax is an Open Source Java Script display engine developed by the American Mathematical Association (AMS) and Society for Industrial and Applied Mathematics (SIAM). It is licensed under the Apache License and supports the rendering of mathematics written in LaTeX or MathML.

The setup is quite easy. If you use a mathematics aware markup parser like kramdown, you simply just add the following java code:

<script type="text/javascript"
src="http://cdn.mathjax.org/mathjax/latest/MathJax.js?config=TeX-AMS-MML_HTMLorMML">
</script>

to an appropriate layout file like _layouts/default.html. If you use the kramdown parser, the input:

$$L = \frac{d^2 \Phi}{d\omega d A \cos \theta}$$

is nicely rendered as:

I’m quite surprised how good the quality of the rendered mathematical symbols is and also I’m surprised how easy it finally was to add this functionality to Jekyll.