One of the problems with gradschoolshopper is that the schools listed pay to be so the "top" programs (Harvard, MIT, Stanford etc.) aren't there because they don't need the additional advertisement.
From the listings however the broad categories with the greatest number of programs appear to be in the areas of Condensed Matter Physics, Atomic/Molecular/Optical Physics, Astrophysics, and Biophysics.
I actually find USNEWS to be a better resource. You can disregard the rankings if you want, but it allows you to narrow down schools based on broad area of study and you can further refine your search based on location if that's a factor that's important to you.