Wikipedia - Wikipedia is a free online encyclopedia, created and edited by volunteers around the world and hosted by the Wikimedia Foundation.
Encyclopædia Britannica - Explore the fact-checked online encyclopedia from Encyclopaedia Britannica with hundreds of thousands of objective articles, biographies, videos, and images from experts.
Editthis - A free wikifarm project allowing to keep private wiki and build it up through MediaWiki syntax.
Kiwix - Kiwix enables you to have the whole Wikipedia at hand wherever you go!
Oppia - Oppia is a free, open-source learning platform.
Wikidot - Online collaborative wiki hosting for organizations,etc.