The best way to deepen your knowledge is to buy books as a complementary. If you were interested by the AI class, for example, a good complement is Norvig / Rus

The best way to deepen your knowledge is to buy books as a complementary. If you were interested by the AI class, for example, a good complement is Norvig / Russell's AI book, and if you want to know more about robotics Thrun's book is excellent as well. For every subject, even highly specialized ones, you can find a 600+ pages book which will cover the basics of that subject. I think people just don't know the amount of quality knowledge you can find in technical books nowadays. You will hardly ever find the same quality material available online — although from time to time you can find freely available PDF drafts or papers, but that is rare. These kind of books cover a lot of depth usually up to near-research level; if you want to dig even deeper you'll have to explore research papers. They (usually) cost between 40 and 80 euros / dollars; if you're on a dire financial situation, check out your local public library (or your university's if you're a student), they will most likely have the one you are looking for.