The best Band on Long Island is a Novelty band Called O' El Amor. Great music and excellent showmanship. They are playing at Katie's in Smithtown NY on 10/30. Anyone who goes will not be disappointed.
A few years back I lived in Manhattan with a few guys who were, and still are, in a band. They're called Mook, and really are quite a treat to see live.
They were at CMJ last year, not sure about this year but more than likely they'll be there.