Church Fathers Scripture Index — Church Fathers Scripture Search Engine (using the CCEL Early Church Fathers digital edition of the Philip Schaff collection).

Early Church Fathers — Online edition of the Early Church Fathers series from Christian Classics Ethereal Library.

Early Church Fathers (Additional Texts) — English translations are all out of copyright, but were not included in the 38 volume collection of Ante-Nicene, Nicene and Post-Nicene Fathers.

Early Church Texts — “One of the most extensive resources on the internet for the study of early Christianity.”

Fathers of the Church — Online collection from New Advent.

Guide to Early Church Documents —  ICLnet pointers to Internet-accessible files relating to the early church, including canonical documents, creeds, the writings of the Apostolic Fathers and other historical texts relevant to church history.

Internet Theology Resources: Church History and Historical Theology — Contains an annotated list of links, arranged chronologically and topically, to texts spanning the history of Christianity. While the number of early Christian texts is modest and quite standard, its large annotated list of links to internet resources for church history and historical theology is very useful.

Internet Theology Resources: Monastic Studies — A very useful page containing texts in both English and Spanish translation, some apparently unique, and a number of interesting photos of monasteries. Again, the annotated links to internet resources on monasticism are very useful.