I've studied programming for a few years now and I have compiled a list of go to places where I learn new concepts (or brush up on basics). The sites I'm going to share are both profit/non-profit but I'm linking them for the free content. I am more of a visual person, so I prefer videos and interaction as my source of learning material.

https://www.khanacademy.org - this is (I think) an NPO that has courses on a wide variety of topics (from math and business to CS and beyond). They have a great CS algo course which was curated by Thomas H. Cormen - his intro to algorithms is on of the most perused books on the topic. They also have great introductory courses on web development and other topics as well as an engaging gamified platform that makes you study with enjoyment. You can also run your own code and save it.

https://www.udacity.com - this website is a joint effort of many of the behemoths of the current industry such as Google, AT&T and others. They have the concept of nanodegrees which are paid, however, they also have free high quality courses as well as sneak peaks to some of their most interesting nanodegrees. They have a discussion forum, exercises built into the course content and a huge variety of topics. I haven't spent money on a nanodegree, yet I have watched at least 50 courses over time and I am very happy with what I've learned.

https://www.coursera.org/ - this is the heavy lifter when it comes to online courses. The courses are on myriads of technical and non-technical topics and are curated by some of the most prestegious colleges in different countries. You can audit almost any course (this means to see the content but not be able to attain a degree) and there are some courses that are entirely free. As this are mainly courses as provided in colleges, you'll have to devote more time and effort to learn, if you want to make use of this site.

https://www.edx.org/ - this site is kind of a hybrid between coursera/udacity. Some of the courses are technology specific - they have a courses on Microsoft tech and blockchain, for example, but they also have many cs and non-tech courses as well. My favorite course would be CS50 by Harvard University. If you have the time to spend - it's really informative and engaging at the same time.

https://www.freecodecamp.org/ - this is an aggregated resource and if you're a front-end web dev it's an indispensible resource of knowledge. You can learn front-end coding just by this one resource.

Honorable mentions

These sites have both paid/free content but I still like:

https://www.pluralsight.com/ - this is THE SITE for professional developers. It has a great variety of pro topics delivered in a very compelling manner.

https://www.codecademy.com/ - this site had a major overhaul and I can't say I like it as much because most of the interesting things are now paid. They have mostly introductory content but it's well structured and has nice interactive UI where you type your code.

This is by no means an extensive list. There are many other sites to learn from like hackerrank, project euler and do on, where you do competitive programming. This is just MY way of studying and keeping up-to-date with technologies.