MediaWiki

If you need your own wiki, MediaWiki (the gubbins behind Wikipedia) is what you want and available in Gaelic too. Don’t worry about that bit mentioning MediaWiki Hackers on their main page – we’re not talking breaking into the Pentagon, it’s just developer talk for someone who is very good at helping develop the MediaWiki further.

You can download it here and there’s a shedload of guidance (in English) available on the project pages.