What are some good textbooks and online resources for learning about geophysics? That is, physics, as it relates to the earth's geology, shape, and internal structure.
There are two universally loved geophysics texts : Turcotte and Shubert and Stein and Wyessesion. Both are upper division/lower graduate level texts. Fowler is great if you do not have a strong mathematical background (multivariate calculus). Beyond that, it might be difficult to get a a good understanding without an Introductory physics course, and a few semesters of calculus. A good way to learn about geophysics, is in fact, just learning about physics and mathematics in general. Hopefully this stack exchange will also become a good resource.
I also strongly suggest the courses available on the coursera platform under the category "Energy & Earth Sciences" here.
Geophysics has many flavors to it. Prof Claerbout's site has a lot of free stuff which are a good introduction to one part of it.