Greek life at Pomona is indeed severely limited. Many wonder why it even exists. It is largely due to the patronage of one Fred Sontag, Pomona philosophy professor, who has always been a strong proponent of frats as a place for young men to, essentially, be young men together. That's pretty much how it works. Kappa Delta and Sigma Tau both host a weekly kegger, but neither have houses of their own. Attendance at the events is generally somewhat limited. Nu Alpha Phi is a coed frat and is responsible for a number of the wilder, stranger campus events, but they don't have a house, either, and they really don't resemble a frat in anything but name.
If you want to be involved in Greek life at Pomona, just don't expect it to be like "Animal House." They may, or may not, be animals, but they don't have a house, so the frats' place on campus is basically limited to their weekly keggers. Sometimes, they hold fundraisers, like the Kappa Delta "buy a date with a Kappa Delta guy" thing. There is a significant handful of nonfrat students who take advantage of the frat events, either for the beer or for the purpose of flirting with frat boys.