Corpus Scriptorum Latinorum
The Forum Romanum website provides a list of Latin literature online, both texts and translations, and includes patristic authors.
EWTN Patristics Library
Another site from which ANF and NPNF may be downloaded. Prefatory notes indicate that EWTN has corrected the texts; they may be more accurate than those posted to other sites.
New Advent: Fathers of the Church
This archive has e-texts of Ante-Nicene Fathers (ANF) and Nicene and Post-Nicene Fathers (NPNF) arranged alphabetically.
Early Church Fathers (Calvin College)
An archive containing all volumes (less indices) of the Ante-Nicene Fathers (ANF) and Nicene and Post-Nicene Fathers (NPNF) in searchable format. All works can be freely viewed online, downloaded for free as text files, or downloaded as pdfs for a fee.
Internet Medieval Sourcebook
The three primary divisions of the Sourcebook are the Selected Sources page which presents a selection of primary and secondary texts chronologically and topically, intended to be a student resource; a Full Text Sources page which groups all archived primary texts by type and period; and Saints’ Lives page devoted to hagiographical texts and resources. The …