Coursera - Build skills with courses, certificates, and degrees online from world-class universities and companies
Golden - Mapping all human knowledge
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.
PalPark - Curate and share your learnings by topics
Udemy - Online Courses - Learn Anything, On Your Schedule
Bookshlf - Content worth sharing