Patristic studies is an area that is experiencing growth among evangelicals, but it’s a field where resources can be difficult to come by. Roger Pearse has an excellent website devoted to the works of Tertullian, including links to online translations of Tertullian’s writings.
Pearse’s site, however, is not limited to Tertullian. Pearse devotes an entire webpage to additional works from the early church fathers (see here). According to a brief statement in the webpage header, Pearse states that the works linked on that page are out of copyright and are not included in the 38 volume Ante-Nicene, Nicene and Post-Nicene Fathers. The works are ordered chronologically. Included on this page are the likes of Polycarp, Aristides the Philosopher, Hermias the Philosopher, Optatus of Milevis, and more.