Wikipedia - Wikipedia is a free online encyclopedia, created and edited by volunteers around the world and hosted by the Wikimedia Foundation.
Golden - Mapping all human knowledge
Miraheze - Miraheze is a wiki farm (hosts wikis) for free and with no ads, it also provides custom domains...
PalPark - Curate and share your learnings by topics
Kiwix - Kiwix enables you to have the whole Wikipedia at hand wherever you go!
Bookshlf - Content worth sharing