All written in PHP - so portable, so incredibly slow...about as fast as the original MediaWiki parser! (For the source, see here, trunk 'wiki2xml', directory 'php')
Known issues:
In templates, {{{variables}}} used within <nowiki> tags will be replaced as well (too lazy to strip them)
HTML comments are removed (instead of converted into XML tags)
This page can be called with parameters: w2x.php?doit=1&whatsthis=articlelist&site=en.wikipedia.org/w&output_format=odt&text=Biochemistry For additional parameters, see here