A lot of online courses for coding skills are available nowadays, both free and non-free. I will collect this kind of websites (ever spent some hours on each one) here.
1. Coursera: Free
A nice MOOC website for various courses, some coding lessons also.
2. codecademy: Free
A coding course website on web programming. I have completed some lessons on it. All courses are interactive and contain pieces of code to each task.
3. Treehouse: Non-free
This is the first one I paid some $$ to learn, though still on a free-trial plan until next month. It has some course other than coding, both design and business, such as how to be a freelancer.
4 codeschool : Non-free
Another non-free coding course website with lesson in more content of programming.
5 Microsoft Virtual Academy: Free
http://www.microsoftvirtualacademy.com
Trainings on Microsoft technologies.
6 imooc（慕课网）: free
这里介绍的第一个中文网站，主要的课程以前端和Java为主。
7. codewar: free