Fandom - The entertainment site where fans come first.
DokuWiki - DokuWiki is a simple to use and highly versatile Open Source wiki software that doesn't require a database.
Editthis - A free wikifarm project allowing to keep private wiki and build it up through MediaWiki syntax.
Wiki.js - An open source, modern and powerful wiki app built on Node.js, Git, and Markdown.
BookStack - An open source knowledge management application that's focused on ease of use.
TiddlyWiki - a non-linear personal web notebook