Treehouse has one of the most comprehensive libraries of educational materials on this list, while also being one of the most relevant.
Not only does it offer a large variety of code courses, but it also offers 'workspaces' for you to try out new projects in your own time, as well as a library with videos of talks from industry professionals. It's the only one on this list to offer an iPad app to continue your learning, too.
You can try a free seven-day trial on Treehouse, and from then on there are two tiers of monthly fees that give users access to all of the site's content.
Codecademy is free and easy to set up. Straight away you can create 'goals' for yourself and find the skills you want to learn. These could range from applicable things like creating a portfolio site to silly, fun things like animating your name or building a CSS galaxy.
Lynda is one of the more popular video tutorial sites. It offers an abundance of content that's constantly added to with new and up-to-date technologies and software. Lynda is a trusted resource that many turn to when they're after a tutorial to pick up a new skill.
Skillshare is a subscription-based service that offers thousands of classes taught by industry professionals. Courses come complete with material that's been created by the instructors, and there are projects for you to apply your skills.
Mijingo is an online learning resource that features step-by-step video tutorials for both web design and development. The courses are cohesive and thorough, and some offer transcripts, starter files and additional resources.
No discussion of online training would, of course, be complete without a mention of Pluralsight. Following an acquisition spree, it now offers the world's biggest online training library.
The company owns Code School (mentioned above), Smarterer and Digital-Tutors. Such is the size of the Pluralsight stable, if it doesn't offer a certain course then it's unlikely anybody does.
Learnable offers an ever growing library of courses and books for web designers and developers. The site's aim is to make learning easy, fun and comfortable. You'll find lessons tailored to everyone from beginners right up to professionals.
Many of the programmes allow you to start for free, so you can try a few modules and see if the course is for you before committing financially. This is a great way to find the right course.
Courses range from free to $300, so no matter what your experience level or budget, it's certainly worth having a look.