In every Ashkenazic synagogue I've seen, the fellow calling up people to the Bima is called a "gabbai." (Which was originally a Hebrew word for "collector", as in Tzedaka collector; I can see how the phrase transitioned.)
What about the synagogue president? I think I've heard "nasi beit hakneset", though in a German-influenced synagogue they had a Mi Shebeirach for the president, referring to him as "parnes" [rhymes with "bar-mace"]-- which can mean "leader" or "economic provider."
I've heard of one Sephardic community (I don't know of which origins) where what we call the Gabbai was called the Parnes, but then saw an Iranian-American synagogue where he was called Gabbai. Can anyone clarify this for me, or add to this?