The Mandaeans are a small sect claiming John the Baptist as their prophet, with unique set of gnostic scriptures, and interesting esoteric rituals like purification rites than may link back 2000 years to Temple times. In the wake of the instability in Iraq many have migrated out of Iraq, with Worcester MA becoming a new center.
For more on the Mandaeans, see:
Buckley, Jorunn, The Mandaeans: Ancient Texts and Modern People, (New York: Oxford University Press, 2002)
Lupieri, Edmondo, The Mandaeans: The Last Gnostics, (Eerdmans, 2002), with extracts from primary sources