This site set the standard for all online church history study resources. Links about to all periods of Christian history including the early church, the roman catholic church, the protestant reformation and the modern church.
This is a newer resource, but offers nearly every text you need to become and expert on literature from the privative Christianity. Early Christian Writings is the most complete collection of documents from the first two centuries with translations and commentary. Includes the New Testament, Apocrypha, Gnostics, and Church Fathers.
This site has always offered a comprehensive set of free online books from all periods of church history. Of special value is their complete editions of the Early Church Fathers. They also have a complete recorded narration of the Greek New Testament available for free download.
This a massive store of information. The content is open source, so be sure to verify your facts. Otherwise enjoy a great free resource for learning about Church History.
This is another treasure of manuscripts from Church History. This free online resource offers many primary sources for the study of church history.