Early Christian Writings
There are a huge number of online texts, written by the early Christian theologians, available for free use in digital libraries. The following links contain material that is not necessarily exclusive, but each link given provides its own unique array of texts.
LIBRARIES:
The Saint Pachomius Library (Orthodox – Dark Ages to Mediaeval period)
Corpus Hermeticum (early Hellenic Christian texts) – potentially heretical!
OTHER RESOURCES AND LIBRARIES:
Digital Library of Classical Texts
A HUGE electronic database of Classical texts:
Another HUGE collection of online mediaeval texts, translated into modern English. Good selection of works on the various crusades.