At first, I thought about editing my previous post, but since it's longer than that one…
After revisiting the texts from the Theoretical Minimum, I found this bit from a Classical Mechanics preface as a rather apt summary of the series:
What became clear after a couple of quarters is that the students were not completely satisfied with the layperson’s courses I was teaching. They wanted more than the Scientific American experience. A lot of them had a bit of background, a bit of physics, a rusty but not dead knowledge of calculus, and some experience at solving technical problems. They were ready to try their hand at learning the real thing—with equations. The result was a sequence of courses intended to bring these students to the forefront of modern physics and cosmology.
IMHO the authors accomplished their job. In the series so far you have gateways to branches of physics you could expand on through other books:
Classical Mechanics by J.R. Taylor
Introduction to Quantum Mechanics by D. J. Griffiths (of Introduction to Electrodynamics fame)
Principles of Quantum Mechanics by R. Shankar
Diagrammatica: The Path to Feynman Diagrams by M. Veltman (quantum field theory in a nutshell, which also happens to be a title of a different textbook that's intended for newcomers :P)
Gravitation and Cosmology: principles and applications of the general theory of relativity by S. Weinberg (disputable choice, but I liked the fact that a lot of the calculations were explicit. Starts with a differential geometry refresher, which may or may not be enough)
Most of those are either from my undergrad courses or ones that I picked up at random at the library and liked a lot.