Fortunately more and more interesting websites to learn programming from scratch or to practice what they have learned: Codecademy, LearnStreet, Code.org, CodeSchool, etc. Unfortunately these sites are not enough for many professionals who require an advanced level in the management of code to apply to practical problems in their respective areas, or simply characteristics of generic feedback are not as rich as if it could be a comment, correction or expert advice.
Well, Exercism.io is a service that reaches for solving such contradictions, in fact, the teacher who gave birth did for a similar situation, because your pupils are encouraged to complete their programming exercises for lack of a constant feedback to guide them to one or more answers to solve specific problems. Thus was created a bright space where experts and novices are considered to work on problems presented by the platform daily arming chains conversations as long as enriching for each user.
Finally, another valuable resource that gives us the web to learn and practice programming, this time at a more advanced level and even more social.