MathML is my own personal winner but two pitfalls present themselves:
(1) Integration with Blogger
(2) Rendering MathML in Internet Explorer requires a plugin (Firefox can render it natively)
Problem (2) is easily solved by ignoring it. If you're stupid enough to (a) use Internet Explorer and (b) can't work out how to install the plugin then you're not going to understand my equations anyway.
Looks like problem (1) can be "solved" in a number of horrific ways, least painful of which seems to be the method described here. Now, if I've implemented it correctly, and you're using a proper web browser you should see a nicely formatted equation below: