Intro
I first discovered Magnus Manske's wiki converter script while searching for a plugin that would simply allow me to output (mediawiki) wiki content to pdf (or text). There is a module that uses an older htmldoc engine to do the conversion, but I would not recommend that plugin. Instead, this plugin is better because it actually deals with the source in a more high-fidelity way (not to mention that htmldoc doesn't seem to be maintained.)
An online demo can be found at http://tools.wikimedia.de/~magnus/wiki2xml/w2x.php The local converter is at Special:Wiki2XML
In fact, that tool is one of many wiki worker tools that Magnus provides, so if you plan to, or already author in a wiki environment, you might want to check out the tools. http://tools.wikimedia.de/~magnus/
Issues
I'm having a read error when doing images, so I'll look into that.
Free Tools for Free Content
The Wikimedia Toolserver has a number of developers and scripts of interest to hardcore wiki hackers. See the toolserver page for more info.