edX

edX is the best free online course website I have found till now.It's the ultimate knowledge treasure. You can learn anything from human anatomy to Astrophysics, from History to Economics and from Maths to Computer Science. And the best part of it is that you can even gen a certificate just for a few bucks.You can learn from the top professors of the top universities like the

1. Harvard University
2. MIT
3. Berkeley
4. Boston University
5. The Queensland University
6. IIT Bombay

and much more. SO, what are you waiting for get started at
https://www.edx.org/

CS50

The CS50 is a full of fun programming learning course.it feels as if you are learning sitting at the Harvard University and it's very interesting. you can learn it at the edX website for free or even get a certificate for just a few dollars.

just check out https://cs50.harvard.edu/           & https://courses.edx.org/courses/HarvardX/CS50x3/
  

SO HAVE FUN & HAPPY INFINITE KNOWLEDGE

KHAN ACADEMY

I don't remember how i first encountered with this website but this was the my first step towards the free education.It's a very good website for anything from maths to history,Biology to computing either you are a school kid who's got problems with understanding your subject or a college student who want's a little extra help, Khan Academy got it. and guess what its fun too all the lectures are followed by workout to make us understand what ever we are learning.so, all the best and happy INFINITE KNOWLEDGE!