I believe paying members have a swap protocol. One of the mods might see this thread and comment. I haven't done an official swap, just shipped beer to people for competition. Some people have PMed each other to meet up and swap that way.
I've done homebrew swaps. I think commercial swaps are less frequent. I'd take Berserker's suggestion. Sites dedicated to commercial beer, like Ratebeer or Beer Advocate might be a better avenue.