Wikifur!

Infogalactic is an Internet-based, free-content encyclopedia project that is a dynamic fork of Wikipedia and improves upon the online encyclopedia's model of openly editable content. Infogalactic's pages are interlinked in order to connect the user to related pages with additional information, and are categorized in a variety of ways, including Relativity, Notability, and Reliability to allow the user to prioritize his personalized perspective

Alchetron.com is a free social encyclopedia for world where you can create, organize and learn easily using topics.

Oppia is a free, open-source learning platform. Full of interactive activities called 'explorations', Oppia helps curious minds learn and teach.

A wiki-based encyclopedia, the primary difference between Citizendium and Wikipedia being that Citizendium has "subject matter expert" editors, chosen by the community to validate pages and content.