Update, This does not seem to work any longer. Any content after the first equation is truncated, so I've removed the script.
I found this post with some information:
http://www.codecogs.com/latex/integration/blogger/install.php
The important feature was to add an HTML/JavaScript gadget with the code found there.
I followed the instructions and it produced this:
\[\int^{+1}_{-1} x dx\]
Which does produce an acceptable equation.
