Early Church Fathers: standard English translations of the two Eerdman's series, the ante-Nicene Fathers, and the Nicene and post-Nicene Fathers.
Библиотека святоотеческой литературы «Patristic Library» from the Blessed Sergius of Radonezh High School, Novosibirsk
The ultra-Orthodox political Web almanac Romanitas (so named not after the See of Rome but after the Synod of Bishops of Moscow «The Third Rome»), mostly in Russian but offering many pages in English as well, hosts many classics: The Great Canon of St. Andrew of Crete [English translation], St. John Damascene, St. Sophronius of Jerusalem, St. Gregory Palamas, Tertullian, the Four Greek Fathers, St. Cyprian of Carthage, St. Leontios of Constantinople, Blessed Ephrem of Syria, St. Maximus the Confessor, St. John of Kronstadt, Blessed Makarios of Optina, St. Ignace Briantchaninoff, etc.
The Ecole Initiative hypertext library of Early Church history.
Christos Sp. Voulgaris, The Biblical and Patristic Doctrine of the Trinity, The Greek Orthodox Theological Review, vol. 37 (Nov.) 3–4, Holy Cross Orthodox Press, Brookline, Mass., 1992.
Christos Sp. Voulgaris, The Church the Body of Christ.
St. Gregory of Nyssa, one of the great Fathers of the Church.
Cyril of Alexandria Contra Iulianos research site (in German).
Pope Pius XII's Encyclical, Orientalis Ecclesiae also speaks about St. Cyril of Alexandria.
Evagrius Ponticus' Thoughts on the Resurrection .
Mysterion and Evagrius on God.
St. Gregory Nazianzen at the Université Catholique de Louvain (excellent links).
George Florovsky, St. Gregory Palamas and the Tradition of the Fathers, Sobornost, 4 (1961), 165–176.
Panayiotis Christou, The Teaching of Gregory Palamas on Man.
St. John Damascene's Exact Exposition on the Orthodox Faith.
St. Maximos the Confessor on Deification.
Peter Charanis, The Monk as an Element of Byzantine Society, Dumbarton Oaks Papers, No. 25, 1971.
Panayiotis ChristouPanayiotis Christou, The monastic life in the eastern orthodox Church, "The Orthodox Ethos", Studies in Orthodoxy vol. 1, Ed. by A.J.Philippou.
The Interdisciplinary Seminar on the Jewish Roots of Eastern Christian Mysticism [ Marquette University, Milwaukee, WI (Jesuit)].
Monasticism: Papers, essays, commentary and exegesis: the asceticism of St. Antony of Egypt, John Cassian, Aphrahat the Persian, Liber graduum, etc.
A History of Early Syrian Monasticism (up to 6th century CE) by Holy Martyr Anatoly (†1938), Metropolitan of Odessa and Kherson [ Orthodox Eparchy of Odessa ] [-in Russian-].
Two works of St. John Cassian, the Conferences and the Institutes were extremely influential on both Eastern and Western monasticism.
For a detailed look at Byzantine Egypt, see the House of Ptolemy site, which contains many patristic texts and information about monasticism.
Dr. Deborah Vess' Medieval Monasticism course at Georgia State University