There are good and bad online instructional platforms for everything: some language courses work better than others and some approaches to teaching music are more effective than others.
This is just as true for computer programming, where, like everything else, an abundance of free courses and tutorials from MIT, UC Berkeley, Harvard and Stanford offer interactive tools for learning web development and computer programming. You can find a long list of free comp sci courses from these great universities here.
One new site that is getting particularly good reviews is Codecademy, a free online learning system for learning everything from HTML Basics to Python in a “user active” style—meaning that users can use tutorials to design projects of their own choosing. It’s also easy to track your progress.
What sets Codecademy apart from other programming tutorials is that all student work can be completed within a web browser. No software downloading or installing is required. Responding to criticism that the site didn't initially offer enough courses, Codecademy has added numerous courses in 2012 and launched a Course Creator program. This is a boon for users interested in learning how to teach. Codecademy does not put user-created courses through an approval process and gives course creators a link that they can distribute as they wish. Codecademy does, however, screen the courses and selects which to feature on its own site.