<div class="math"> avound the user's code, then call
jsMath.Process(document);at the end of the page.
I think mathjax would be the best option. This is the math rendering engine used in mathoverflow.
I've updated Jason Blevin's pandoc plugin to permit tighter integration between Ikiwiki and Pandoc. Given the features Pandoc has added over the past 6-12 months, this makes for a very powerful combination, e.g. with code block syntax highlighting and lots of options for how to process and display inline TeX. Both jsMath and MathJaX are supported, along with many other methods. See https://github.com/profjim/pandoc-iki for details. --Profjim