Many of the texts are onsite here and unique in the web. Also includes German, English, and Greek literature. Bibliotheca Latina - From the University of Wisconsin.
Page is entirely in Latin.
Unfortunately, all but Boethius' Consolatio Philosophiae are restricted to use by students at the University of Virginia. Labyrinth Latin Library - A collection of ancient and medieval Latin texts, but some gopher links are outdated. Pliny's Natural History, Frontinus, Vitruvius, Ptolemy's Geography. Latin Literature - Massive table of Latin literature available on the 'Net in Latin and in translation. Layout is a bit daunting, but there's a LOT of texts here.