Khan Academy is a massive player in the online learning space. It offers tons of learning material for people of all ages. Everything is free, so there’s no need to worry about any upsells at the end.
Mozilla Developer Network
Udacity offers self-paced courses that are always available so that you can take a course whenever you want and study at your own pace. Although the classes are free, the site’s Nanodegree certification and tutoring program are costly, running approximately $200 per month.