BioQUEST found a great way to add equations to a blog–an absolute must for a quantitative post:
<div style=”text-align:center;width:100%” ><img src=”http://www.mathtran.org/cgi-bin/mathtran?D=3;tex=ex%3A%20%5C%3B%20%5Cfrac%7B1%7D%7B3%7D%0A%20%20%20%20%20%20%20%20%20%20%20%20″ alt=”ex: ; frac{1}{3}
“/></div>
The website is http://point.pt/~guillaume/latex/latexiframe.html
All you need to do is write the equation in LateX, convert to HTML, and copy the HTML into your blog.
Another website is http://www.codecogs.com/components/equationeditor/equationeditor.php
It has an easier editor to write equations, similar to Word’s equation editor, i.e., point and click on symbols and it will figure out the correct LateX language.