Other posts on this topic clearly outdated and very strongly polarized/opinionated. From the perspective of a rising junior on the year that just passed–
Castle - international and very wealthy, amazing chapter house
Zetes - similar demographics to castle, but smaller and nerdier
Phi Delt - very stereotypically fratty, many southerners, many athletes, very preppy, great chapter house
SAE - lots of atheletes, demographics similar to state school frats, pretty fratty
Kappa Sig - very strereotypically fratty, many sourtherners, incredibly preppy
OZ - Offcampus, grueling pledging, generically fratty demographics
Pikapp - demographically similar to state school frats, pretty fratty, bad relationships with school (likely to go off campus), dont own an oncampus chapter house
Owls - offcampus version of castle/zetes
Theos - offcampus, mostly rich jews/WASPy kids from top private schools, very fratty
A’s - very WASPy, many ex-athletes who quit because of notoriously bad pledging
Beta - many athletes, pretty stereotypically fratty, lower-tier version of As/phiDelt/SAE
ZBT - almost exclusively jewish
AEPi - exclusively jewish, just got rechartered
APES - offcampus, mostly tristate area jews, great party scene
TEP - relatively alternative, not stereotypically fratty, diverse brotherhood
Sig Chi - lots of athletes, similar to beta and As.
Sammy - very jewish
Pike - small pledge class, still recovering from probation
Phi Psi- nerds
Sig Ep- diverse brotherhood, rising with more recent pledge classes, not stereotypically fratty
DKE- almost exclusively athletes, lots of sprint football kids
ATO- almost exclusively athletes, lots of wrestling kids
Pi Lam- co-ed, very alternative, very diverse, very open minded
Elmos- smaller and more exclusive version of pi lam