Some configurations may be popular, but there's no "standard". The threaded portions of barrels may differ in diameter, thread pitch, and even whether they have left- or right-handed threads.
EDIT - I think the TacSol barrels are threaded 1/2" by 28 threads per inch, which is fairly common, although not enough so to be called "standard".
The threaded portion of the Walther P22 barrel is 8.0mm X .75 mm per thread, but there are adaptors available for it that will let you mount a 1/2" X 28 TPI suppressor.
Last edited by ScottRiqui; February 14, 2013 at 10:39 PM.