1. Swayam- https://swayam.gov.in/
2. NPTEL- https://onlinecourses.nptel.ac.in/
3. Mooc- http://mooc.org/
4. Edx – https://www.edx.org/
5. Coursera- https://www.coursera.org/
6. Udacity – https://in.udacity.com/
7. Udemy – https://www.udemy.com/
8. Khanacademy – https://www.khanacademy.org/
9. Skillsahre – https://www.skillshare.com/
10. Harvard University – https://online-learning.harvard.edu/
11. Ted – https://ed.ted.com/
12. Alison – https://alison.com/
13. Futurelearn – https://www.futurelearn.com/
14. Web Development – https://digitaldefynd.com/best-free-web-development-courses-tutorials-certification/
15. Digital Marketing – https://digitaldefynd.com/best-free-digital-marketing-certifications/
16. ios app development – https://digitaldefynd.com/best-ios-app-development-course-tutorial/
17. Open Learn – http://www.open.edu/openlearn/
18. Future Learn – https://www.futurelearn.com/
19. Tuts Plus – https://tutsplus.com/
20. Open Culture – http://www.openculture.com
Most of these courses are free to learn.