I have just enabled MathJax for the whole site - this means you can use LaTeX, hopefully everywhere (in the wiki, in the blog, etc.). Just use

\( a > 0 \)

for inline expressions, and

$$ a^2 < 0 $$

for display-style equations:

If \( a > 0 \), then $$a^2 < 0.$$

You can play around with it in the other Sandbox (which has the advantage that it can be saved). Let me know if you encounter any problems.