MediaWiki is a free web-based software application written in PHP with a backend database. It was developed by the Wikimedia Foundation and it also runs projects such as Wikispecies and WikiMediaCommons. It is the wiki tool used for WikiPedia. There are numerous extensions available for adding capabilities to MediaWiki (see http://www.mediawiki.org/wiki/Category:Extensions).
NOAA’s GEO-IDE Guidelines and Best Practices Wiki https://geo-ide.noaa.gov/wiki/index.php?title=Main_Page