Catholic Encyclopedia: Tertullian: Long article on this ecclesiastical writer.
Early Church.org.uk: Tertullian of Carthage: Overview of Tertullian's contributions, methods of exegesis, rhetoric, anti-intellectualism, and Montanism. Includes sources.
Excerpts from Tertullian: Comprehensive collection of citations from the Carthaginian writer, arranged by topics and subtopics.
Tertullian On Fasting: Survey on individual, communal, and stational fasts in Tertullian's Carthaginian community.
Tertullianus, Quintus Septimius Florens: Extensive entry on Tertullian encompasses his life and theological notions, and includes outlines of his tracts. From the Early Christian Writings.
The Development of the Canon of the New Testament: Tertullian of Carthage: Tertullian's citations of New Testament writings and other related works.
The Ecole Glossary: Tertullian: Brief biography, by Elise M. Bender.
The Tertullian Project: Information about this second-century church father, his works, lost works, manuscripts.