MOOCs.

They’re free unless you want a “certificate”, which has no practical value and is mostly useful if you want to motivate yourself a bit more and want to support their business model.

Go browse Coursera and edX and learn to your heart’s content.

Also, if you’re coding, watch recordings of conferences about your programming language, e.g. CppCon/C++Now/CppNorth for C++, PyCon/PyData for Python etc…