Always wanted to brush up your knowledge of quantum physics? Geometry? Linear algebra?
There are two cool resources for you:
If you’re more interested in computer science (theory, operating systems, networks, distributed computing), visit udacity.
For more general topics, go to Khan Academy.
Both are YouTube based services which kind of follow school: You get a video with a presentation about a topic. Both sites then offer additional material, Q&A forums, etc.
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