Omega Sigma Tau Omega Sigma Tau: Service and social fraternity established at UCLA in 1966. (O) http://www.omegasigmatau.com/
Omega Delta Sigma Omega Delta Sigma: Local fraternity for military veterans attending the University of Florida, Saint Leo University, and Santa Fe Community College in Gainesville, Florida. (O) http://grove.ufl.edu/~omegadel
Omega Phi Alpha Omega Phi Alpha: A local men's fraternity founded in 1921 at University of the Pacific. (O) http://www1.uop.edu/student/opa/
Omicron Pi Omicron Pi: Local sorority founded in 1987 at Stevens Institute of Technology in Hoboken, New Jersey. (O) http://attila.stevens-tech.edu/bherc/opi.html
Omicron Pi Omicron Omicron Pi Omicron: A local men's fraternity founded in 1903 at Clarkson University in Potsdam, New York. (O) http://www.clarkson.edu/~opio/
Onyx Onyx: African-American honor society founded in 1974 at the University of Pennsylvania. Overview, history, and member list. (O) http://dolphin.upenn.edu/~onyxhs/
Omicron Gamma Omega Omicron Gamma Omega: Local men's fraternity founded in 1966 at Millersville University. (O) http://marauder.millersville.edu/~ogo/
Omicron Xi Alumni Omicron Xi Alumni: For sisters and alumni of this local sorority at SUNY - Oswego to keep in touch via bulletin boards and photo albums. (O) http://pages.ivillage.com/dejabruce/omicron.html
Omicron Epsilon Pi Sorority Omicron Epsilon Pi Sorority: A national sorority for lesbians of color, founded September 21, 2000. (O) http://www.geocities.com/omicron_epsilon_pi_inc/