The regular use of Omar as a given name in North America undoubtedly is because of the fame of the Persian poet Omar Khayyam. His "Rubaiyat" has been widely read in English translation for hundreds of years. In modern times his first name is often written as Umar, as it is on this site, but during the 19th and early 20th centuries he was almost invariably referred to as "Omar" in the USA.
Also, there was a Libyan Resistance leader against the Fascists named Omar Muktar. About him here: http://en.wikipedia.org/wiki/Omar_Mukhtar Interesting movie about him too.
This is the name of one of Osama Bin Laden's sons. He runs his own scrap metal business in Jeddah, and is married to an Englishwoman 24 years older than him.
Omar Sharif (born Michael Demetri Shalhoub in 1932) is an Egyptian actor who has starred in Hollywood films, most famously in Doctor Zhivago, Funny Girl and Lawrence of Arabia. He has been nominated for an Academy Award and has won three Golden Globe Awards. Omar El-Sharif is the name he chose when he converted to Islam.