It would be good if one could separate these lists into free online material and links to online bookstores. Also, it would be nice to list popular and semi-formal material separate from real rigorous stuff, or to add some annotations to that effect.

Regarding quantum theory, these are the best introductory online materials I've found:

• Quantum Mechanics and Philosophy: An Introduction by Ezio Vailati. (A gentle introduction, with lots of philosophical talk, but still presented using no-nonsense math.)

• Consistent Quantum Theory by Robert Griffiths. (Rigorous, but limited to toy models in finite-dimensional Hilbert spaces. Presented using the consistent histories approach. Makes a good job of clarifying some points I found awfully confusing elsewhere.)

• "Quantum Computing since Democritus" course notes by Scott Aaronson. (Lots of fun to read, semi-rigorous, touches on many computability/complexity/foundations topics.)

Also, general relativity isn't really discussed here much, but still, here are some online materials I can recommend, so you can consider adding that to the list:

• Lecture notes by Stefan Waner. (Basic introduction, rigorous. The best free online text I've seen.)

• Lecture notes by Sean Carroll. (Basic introduction, rigorous.)

• Tutorial by John Baez. (A casual, semi-rigorous tutorial that developed out of an old online discussion. Excellent for building up intuitions when used alongside a more rigorous text.)

• Lectures by Leonard Susskind. (Basic introduction, rigorous. A very good lecturer.)