For some reason, I keep going back to mechanics as a starting point for my various studies. At this point, I am talking about mechanics as a division of physics.
There are several subjects that can be included in mechanics. Originally, this term had to do with machines, as in levers and screws, but with the addition and emphasis of other subjects, the meaning began to change. I recognize four principal areas.
1) Classical mechanics. This includes studies of particles, rigid bodies, and deformable bodies, including gases and fluids. This still is the most common and useful area of study. Before the 20th century, nearly all mechanics was classical mechanics.
2) Gravitation. This is usually included in classical mechanics, but it doesn't neatly fit within another organization of the subject, so I have separated it out.
3) Relativity. This deals with corrections which are needed to classical mechanics in the cases of very high speeds and strong gravitational fields. Since these are outside the realm of everyday experience and require some advanced mathematics to fully comprehend, I will not develop it in great deal.
4) Quantum mechanics. This deals with the corrections that are needed to classical mechanics in the case of atomic-sized and smaller particles. This is more applicable, especially in chemistry, but involves even more advanced mathematics, and I will set aside discussion of this subject as well.
There are some connections to electromagnetism and the structure of matter, and a few connections to thermodynamics, but for the most part, mechanics is considered more fundamental than these other subjects. Chemistry is useful when the particular properties of specific substances are important. Astronomy, earth science, and biology are useful for examples and illustrations. There are comparatively few people who specialize in mechanics as an area of theoretical study. It is somewhat difficult to find internet resources at an intermediate level of study, and this is most easily approached by examining general physics textbooks. It requires a fairly high level of mathematics, and is more closely associated with education than any of the other social institutions. The communities and peoples involved and the history of mechanics are also useful, though it can be difficult to find an introductory account of the history of mechanics.
My interest in the subject is more mathematical and theoretical than experimental, although what resources to suggest depends heavily on how much you already know.