Forum Romanum presents an online library of Latin literature and online versions of several public domain scholarly works on Roman life, medical technology, and history.
The Decline and Fall of the Roman EmpireJohn B. Firth's Constantine the Great: The Reorganization of the Empire and the Triumph of the Church covers Roman history from Diocletian through Constantine, and includes discussion of the Arian heresies.
The Roman Law Library presents translations of Roman laws, edicts, decrees, letters, and codes, including the Twelve Tables. Click on "Lingua Anglica" for the English versions.
The University of Virginia presents "The Ovid Collection," which includes texts and illustrations from various modern and Renaissance versions of Ovid's Metamorphoses.