Friend(s) of Dorothy (FOD) was a slang term used within the LGBT* community of the '50s. Judy Garland was one of the first celebrities to embrace her gay fans and the Wizard of Oz was viewed as a “gay” fairy tale for many queer Americans at the time. The phrase was often used as the password to enter gay establishments.
I think it's safe to describe "Queer As Folk" as one of the most important LGBT TV shows in the history of television. While the original UK series only lasted two seasons, the US version lasted five seasons. The show was renowned for it's depiction of sex and drug use and controversial story lines. It was incredibly well made show - definitely a MUST watch!!