We all know it is the undisputed winner when it comes to learning via interactions. It has an easy to use interface with some great course contents. Course is well structured and the tour of the site will not waste even a second of yours. Rather, from introduction page itself, you will smell some coding and you get the feel of effective online learning. There are panels; one directs you and makes you understand the coding and other allows you to test what you learn. You write the acceptable code and can run it to check for its correctness.
Unlike code Avengers and Codecademy, Code School provides you some mind-blowing learning but with some cost. Intermediate level is free but hard level that will test your water is worth $25.
Sometimes reading plain text can be boring and in such cases, videos are the best help you get at Udacity. Videoed lectures with some mind-blowing quiz will take you another world of interactive learning. An online learning platform teaches a plethora of programming and web design skills. You get courses range from beginner to advanced levels. Not only this as soon as users finishes their course they also get rewards and badges.
If you want to have some fun where multiple people can compete and learn at the same time then you must try Code Racer. It is multiplayer gaming opportunity once you want to polish your skills.