Miraheze - Miraheze is a wiki farm (hosts wikis) for free and with no ads, it also provides custom domains...
Fandom - The entertainment site where fans come first.
Wikiful - Wikiful is an online platform that makes it easy to build and share a wiki.
Editthis - A free wikifarm project allowing to keep private wiki and build it up through MediaWiki syntax.
BookStack - An open source knowledge management application that's focused on ease of use.
Everipedia - The world's largest english encyclopedia