Codecademy

codecademy.com

Codecademy is a free web and mobile-based platform that teaches employable digital skills to millions of users worldwide. Through its platforms, learners discover concepts such as HTML/CSS, Javascript/jQuery, Python, Ruby, PHP, and APIs by actually building things and getting constant feedback from peers. Codecademy is an entirely new, networked approach to learning in which you interact with students across the globe, build amazing projects.