The proudest moment of my Barbershop quartet career (and also the one that sounded the best) was when I sang on stage with Realtime, the 2005 Barbershop Quartet International champions, in Indianapolis in July 2006.
I sang for a few years in a Barbershop quartet called "Ignition!" (we even finished in the top 10 and won the award for Best New Quartet at the 2003 Australian championships), and with two Barbershop choruses: Sydney Harmony and The Brisbane River City Clippers.
I have built websites for about a dozen Barbershop choruses (and other singing groups). They are listed here.