MediaWiki - MediaWiki is a free software wiki package written in PHP, originally for use on Wikipedia.
DokuWiki - DokuWiki is a simple to use and highly versatile Open Source wiki software that doesn't require a database.
PukiWiki - PukiWiki is a functional and reliable wiki software that has been widely using for Japanese wikis and is using the PHP framework.
MDwiki - Static single file CMS/Wiki done purely with client-side Javascript and HTML5.
Tiki Wiki CMS Groupware - Tiki Wiki CMS Groupware, also known as Tiki (or TikiWiki), is a full-featured, web-based, multilingual, all-in-one Free/Libre Open Source Software solution. Tiki can be used to create all kinds of web apps, portals, knowledge bases, intranets, etc.
PhpWiki - PhpWiki is an all-in-one web-based application that was used as a clone of WikiWiki web but now has been used to edit and format books for publication.