I just tried installing the iTeX2MML plugin from Jacques Distler. This is what the n-Category Cafe use for their mathematics, and it gives a neated display than the LaTeXrender plugin I've been using so far.
It turns out, though, that
1. The plugin jumps on quoted perl code, interpreting it as mathematics. Bad things ensue.
2. It needs valid XHTML, which has not been a priority so far - and trying to validate it, the validator chokes on the &'s in my LaTeX array expressions for LaTeXrender.
Oh bugger. No iTeX and MathML for me.