For the more mathematically inclined, I recommend the lectures by Barak Shoshany, who taught the summer version of PHY256 and took a much more rigorous, math-y, approach than I will: e.g., Mathematical Background Part I [if you are more comfortable with a high degree of rigour, I also recommend the first chapters of Shankar's book, listed on the Readings webpage.]
Here are some short notes about adding and taking the absolute square of complex amplitudes, which may prove helpful.
Here is the online simulator of the Stern-Gerlach experiment.
It may still have some bugs, but it gets the basic ideas across.
Suggestion: try to create the equivalent of the three-polarizer experiment you saw on video, but for atoms.
Photoelectric effect from Khan Academy (too much detailed arithmetic done on a calculator for my tastes, but good to see how the sausages are made at least once)
