APT
Official website of the Rome Tourist Office.
http://www.romaturismo.com/

Coinsociale.it
A list of tourism offices around the city.
http://www.coinsociale.it/tourism/accessiblerome/punti_informativi.php

Compagnia Italiana di Turismo
CIT is an international network of travel agents promoting Italian tourism. The organization has offices in America, Canada, Australia and the UK, among other locations.
http://www.citspa.it/

Comune di Roma
Official website of the Rome's municipal government. In Italian only.
http://www.comune.roma.it/

ENIT
Website of Italy's state tourist board.
http://www.enit.it/

Enjoy Rome
An unofficial, but useful, guide to Rome.
http://www.enjoyrome.com/

Italia
The North American homepage of the Italian Government Tourist Board contains links to regional tourist office websites.
http://www.italiantourism.com/

Provincia Roma
The Italian-language website of the authority responsible for the province of Rome.
http://www.provincia.roma.it/

Regione Lazio
Italian-language guide to the region surrounding the capital city.
http://www.regione.lazio.it/

Turismo Lazio
Official tourism information website covering the Lazio region, of which Rome is a part.
http://www.turismolazio.it/
http://www.turislazio.it/

Vatican.va
Official website of the city state.
http://www.vatican.va/