I found some writings of church fathers at Elpenor's Home of the Greek Word
It includes some writings of Origen, Ignatius, Gregory of Nyssa, Symeon and others. It also includes earlier greeks like Homer, Plato, Aristotle, etc.
Also, LATO (Library of Ancient Texts Online)
has a lot of good stuff, although the church fathers seem to be grouped into a single "Church Fathers" category and all the links lead to translated works.