Wikipedia - Wikipedia is a free online encyclopedia, created and edited by volunteers around the world and hosted by the Wikimedia Foundation.
V for Wiki - A beautifully designed Wikipedia app for iOS
Miraheze - Miraheze is a wiki farm (hosts wikis) for free and with no ads, it also provides custom domains...
Kiwix - Kiwix enables you to have the whole Wikipedia at hand wherever you go!
WikiGalaxy - Explore wikipedia in 3d
Oppia - Oppia is a free, open-source learning platform.