Editthis - A free wikifarm project allowing to keep private wiki and build it up through MediaWiki syntax.
Investopedia - Investopedia has a lot of information to share with business mind people.
Fandom - The entertainment site where fans come first.
Miraheze - Miraheze is a wiki farm (hosts wikis) for free and with no ads, it also provides custom domains...
Wikiful - Wikiful is an online platform that makes it easy to build and share a wiki.
FactBites - FactBites is a kind of search engine whose information sharing system is just like that of web-based encyclopedias.