One of the most important primary sources on the early church was included in the Perceus collection - namely the letters of Pliny the younger. Unfortunately, they are in Latin only, for whatever reasons. This brief letter (and Trajan's briefer reply approving the policy) is a witness to how Romans saw the Christians at the beginning of the 2nd Century, what persecution was like, and hints of the worship and Christology of the early church.
Anyway, I was wandering around http://www.earlychristianwritings.com and found a clean translation of these letters and tagged them with the Pliny datatype.
SDG
Ken McGuire