MIT has OCW
which is awesome.
Searching directly Youtube can turn up various coures/lectures on material. Of particular note is stanford universities channel, which has some good stuff on modern physics and programming (as well as a few other things that aren't of interest to me). Theres plenty of much shorter and of potentially worse quality things on youtube as well which can be a bit discouraging, but theres good stuff to be found if you wade through it.
ETA: I should also point out there is a sticky full of science websites (including OCW) that is pretty much designed for your question. Although to be fair, a number of those sites are more references then full guide/courses to learn from scratch, but they're still worth going through to find what suits you.