I'm now beginning to find others on the world wide web who are family either in the "tighter" sense of known cousins, etc., or in the "looser" sense of researchers following up interconnected lines. Here are their various websites (in no particular order).

• Zangerl & Allied Families:
  Carol Zangerl contacted me out of the blue and, after the exchange of a few notes, it would seem that there is indeed a connection between our lines. "Zangerl" would appear to be the "root form" of the name, although church records from Kappl in the 1600s were already adding an "-e," an "-i," or even a "-y" at the end (for the masculine forms; the feminine form seems to have been a consistent "Zangerlin"). Anyway, Carol's page offers some information for the period before the late 1600s that is relevant for my research.

• Singerline Home Page:
  Ryan Singerline maintains this website about his family. If I have it figured out correctly, Ryan is my second cousin, once removed (his father and I are second cousins, as our fathers are cousins, and our grandfathers were brothers).