Some LaTeX geeks (like me) have always been frustrated at our inability to send complicated yet legible equations over e-mail. Most resort to sending raw LaTeX input, but that gets very old -- decyphering
\sum_{n=1}^{n}\pi\frac{e^{n}}{1-K} (or whatever) on the fly is a pain.
Imagine my delight when I discovered EquationService, a neat little service that transforms LaTeX code directly into a miniature PDF graphic embedded in your mail. And, hats off to the author, it's free!
Mac OS X Hints
http://hints.macworld.com/article.php?story=20030831000153525