virgil.org
Aeneas in Italy
Detail from "Aeneae Trojani navigatio ad Virgilij sex priores Aeneidos," in Joseph Warton et al., The Works of Virgil, in Latin and English (London, 1753).

virgil.org
The Underworld
From Andrea de Jorio, Viaggio di Enea all' inferno ed agli elisii secondo Virgilio (3rd ed.; Naples: Fibreno, 1831). Interprets the various sites in Virgil's underworld in terms of the real geographical features of the place. Also recommended, on the geography and archaeology of Cumae: Raymond V. Schoder, S.J., "Vergil's Poetic Use of the Cumae Area," Classical Journal 67 (1971-72): 97ff.

Carlos Parada
The Underworld
Traces and compares the journeys of Odysseus and Aeneas.

l'Université de Caen
Le plan de Rome
Paul Bigot's (1870-1942) plaster model of Constantine's Rome (c. 300 AD). Many views, with extensive commentary and bibliography for most sites. Thematic and historical tours also available. Searchable by keyword.

Janet Burns, About.com
Public Domain Maps of the Ancient World
Public domain is something of a misomer here, since commercial use is not permitted for some of them. Non-commercial use, is free, however.

Leslie Flood et alii
Forum Romanum
Clickable map with photographs and prose descriptions. Also includes a list of literary references to sites in the Forum (though none from Virgil).

Tufts University
Perseus Atlas
Atlas of ancient Greece and Rome, navigable by clicking on an area of the map or entering a place name.

N. S. Gill
Maps of Ancient and Classical History
Links to maps of ancient Africa (including Egypt), Asia, Greece, Mesoamerica, the Near East, the Roman Empire, and the Underworld.

Bill Thayer, University of Kansas
LacusCurtius: Into the Roman World
Don't be put off by the ugly pink background (which I'm told looks better on Macs). This page links to extensive sites you won't find elsewhere, including the Roman Gazetteer (76+ pages with 224 images), a Roman Atlas (some of it indexed), Pliny's Natural History (cross-referenced with the atlas and gazeteer), and Ptolemy's Geography. Now searchable, with even more content: Frontinus de Aquis on the Roman water supply, Vitruvius on architecture, Q. Curtius' Histories of Alexander the Great with Theodor Vogel's apparatus criticus, Rodolfo Lanciani's Pagan & Christian Rome, Codrington's Roman Roads in Britain, a Latin inscription primer in quiz format, William Smith's Dictionary of Greek and Roman Antiquities, and Samuel Ball Platner's Topography of Ancient Rome.