http://meta.wikimedia.org/wiki/Wikitrans_(MediaWiki_Extension)
Wikitrans is a MediaWiki extension that enables full machine translation support for MediaWiki during editing and PHP article generation. Wikitrans converts and translates wikitext into a target language in HTML output through MediaWiki, while retaining and saving the original English text in the body of the Article. Wikitrans renders and translates the wikitext dynamically into HTML when the article is saved in the database.
Sample Pages at Wikigadugi: (you can edit and test drive it with MediaWiki)
http://chr.wikigadugi.org/wiki/%E1%8F%97%E1%8E%A6%E1%8E%B4%E1%8F%B4%E1%8F%97...
I still have a lot of performance optimization to do, but the first cut seems to work well with Cherokee.
Jeff