Christian Heresy - - Short descriptions of Gnosticism, Montanism, Monarchianism, Arianism, Apollinarianism, Nestorianism, Eutychianism and Pelagianism.
Christian Heresy - - A general Wikipedia article which also contains some heresies later than the early church period. Heresies are grouped into a number of categories, such as Christological, institutional, textual, and other.
Classic Heresies - - Short descriptions of Arianism, Docetism, Ebionitism, Pelagianism, Eutychianism, Nicolaitanism and Montanism.
Forms of Christianity in its First Centuries - - A history of Christianity starting with Jewish converts, the Nazarenes and Ebionites, then Arians, Marcionites, Gnostics, and finally the victory of (modern) Cappadocian-Pauline-Nicene Christianity from 380CE onwards.
Heresies, Authority, Quarrels and Words - - An account and analysis of belief systems declared heretical by the Catholic Church. Site is sharply critical of authority and religion, and especially of the Church.