My undergraduate education was a little lackluster compared to what was required by the PGRE (went to a small liberal arts school), so I too prepared heavily for the test. Here is what I studied:
Optics - I used "Optics" by Hecht. Optics was my toughest subject because i actually didn't take a course on it, so I knew embarrassingly little about it (I never even learned geometrical optics). You can pick and choose the chapters that address what's on the PGRE (there's a chapter on wave properties, one on diffraction, one on geometrical optics, etc), so you don't have to read the entire book to learn what you need.
Quantum - I used Griffiths, and felt very strong in my quantum abilities. Know the solutions to the 1-D Schrodinger Equation inside and out, for common potentials such as the infinite and finite square well, harmonic oscillator, dirac-delta, free particle, etc. These can all be solved with a competent grasp of differential equations. Be familiar with the wave functions, energy levels, and expectation values of observables for all these potentials.
Arguably even more important, know the solution to the hydrogen atom. This is essentially the coulomb potential (1/r) applied to the 3-D Schrodinger Equation. The full derivation is extremely lengthy but the math is completely within the understanding of a bright undergraduate, so I recommend taking the time to solve the solution yourself. Know the equation for energy levels of the hydrogen atom, the three “variables” of the wave function (n, l, and m), the properties of angular momentum inside an atom, and spin (especially for spin-1/2 particles such as electrons).
Know the bra-ket mathematics of formal quantum (it’s the notation that looks like <a|a>, etc). Several laws arise out of this, such as the uncertainty principle, which you should know. Know the basics of perturbation theory and multi-particle systems, and how the latter implies the Pauli Exclusion Principle for fermions.
Atomic – Atomic is really just applied quantum, if you thoroughly read up on quantum you should pick up all the atomic knowledge you’ll need. Things such as energy levels of the atom, the structure of the periodic table (and how it relates to the n,l,m values of the wave function), emission spectrum, etc.
Specialized Topics – Read the first chapter of “Elementary Particles” by Griffiths. This will be all the particle physics knowledge you need. I never learned solid state, but you should gain some basic knowledge on this topic as well. It’s mostly factual stuff, such as “what is a cooper pair?”, etc.
Laboratory Methods – use this link: http://www.rit.edu/cos/uphysics/uncerta ... part2.html
to learn about how to add errors/uncertainty. Also, sometimes I think they clump knowledge of circuits into “lab methods,” so know the properties of more advanced circuit elements such as op-amps, transformers (there was a transformer question on the Nov 2012 test), diodes, etc. Also, learn about basic logic gates (link: http://www.play-hookey.com/digital/comb ... gates.html
). Other than that, there’s sometimes questions on how to read oscilloscopes and log-log graphs, but I assume you know how to do that (read up if you don’t).
Right after graduating from undergrad, I knew enough to maybe score a 650-700 on the PGRE. After some heavy studying of the following books/topics listed above, I ended up scoring a 960 this past November. Hope this helps!