New Advent: The Catholic Encyclopedia
This is an online version of the old Catholic Encyclopedia (New York, 1907-12), which contains many articles on early Christian topics.
Resources
Internet Medieval Sourcebook
In addition to numerous ancient texts, the Internet Medieval Sourcebook also provides useful indices and supplementary material, such as select Secondary Sources and Maps and Images.
Athanasius Werke
Website operated by members of the team responsible for the ongoing publication of the Berlin edition of Athanasius’ corpus (Athanasius Werke). It provides information on that project and a bibliography of Athanasian scholarship beginning from 1997.