http://www.hotscripts.com/search?q=glossary&cat=PHP
here are a bunch
There's also a quite neat plugin for joomla, can dig it up if you like or, if you can wait a couple of weeks, I am needing one for a project of mine, and I'm going to build it myself, will pretty much go the simple route really, but if you're looking for something specific tell me, it might cover that