Coursera - Build skills with courses, certificates, and degrees online from world-class universities and companies

Wikipedia - Wikipedia is a free online encyclopedia, created and edited by volunteers around the world and hosted by the Wikimedia Foundation.

Khan Academy - Khan Academy offers online tools to help students learn about a variety of important school subjects. Tools include videos, practice exercises, and materials for instructors. Read more about Khan Academy.

Kiwix - Kiwix enables you to have the whole Wikipedia at hand wherever you go!

Udemy - Online Courses - Learn Anything, On Your Schedule

Miraheze - Miraheze is a wiki farm (hosts wikis) for free and with no ads, it also provides custom domains...