Moonshadow Visions - Excellent hangout of awakening spirits. Not limited to Ishmael readers, but certainly in line with the same goals. Some extremely wise people here as well.
Atlanta Leavers - An Ishmael group in Atlanta.
Ishmael Guestbook - The guestbook on the Ishmael site is not threaded, but there are always interesting conversations going on.
Bay Area Ishmael Group - While not really a forum, they do have regular meetings to talk about things including the concepts introduced in Ishmael.