mathtex is a cgi program that lets you easily embed LaTeX 
math in your own html pages, blogs, wikis, etc. It parses a 
LaTeX math expression and immediately emits the corresponding 
gif (or png) image, rather than the usual TeX dvi.

The following is just an example of use copied from the homepage:
<img src="/cgi-bin/mathtex.cgi?f(x)=\int_{-\infty}^xe^{-t^2}dt"
    alt="" border=0 align="middle">

CGIDIR defaults to /var/www/cgi-bin, but pass a differnet value
if your local installation needs something else.