sociology is a weak theory field which means the canon is pretty contested, to the extent that there is one.
I would start by reading whatever subfield you're planning to specialize in and go from there. Ideally you'll read substantive work and not methods stuff, since the admissions committee probably will be more concerned with your substantive background than aptitude for methods.
If you're interested in doing mathematical sociology, James Montgomery at Wisconsin used to teach a nice two-semester course on this. You might be interested in reading through his syllabus and also reading the articles that have won recent awards from the ASA Mathematical Sociology section.
There's a recent Annual Review of Sociology piece that covers computational methods and one of the sections is on its applications in economic soc/orgs. If you just search for Economic Sociology and Organizations. Networks stuff is also related to computational soc and there's a ton on networks and organizations.
I don't know exactly which works are the best for you to look at but if you're interested in orgs and econ soc I can suggest some names to check out: Mark Mizruchi, Frank Dobbin, Martin Ruef, David Stark, Greta Krippner, Neil Fligstein, Heather Haveman, Brian Uzzi, Joel Podolny, and Howard Aldrich.
Also, it's worthwhile to read the work of faculty at places you might want to apply to, just to see if you like their work. Based on your interests you might want to check out faculty who look interesting at Harvard, Duke, UCLA, Princeton, Arizona, Cornell, Michigan, Columbia. Listed in no particular order.
Some others on the bubble...Northwestern is kind of a tough call, since they have a ton of great econ soc people but only one networks guy. Washington might be okay. Maybe Ohio State too? UMass?
I would stay away from Chicago based on your interests.