ACM Sigmobile
Contains the contact numbers of several radio taxi companies in Rome.
http://www.sigmobile.org/mobicom/2001/general_info.html

My Travel Guide
Advice on getting around Rome by taxi.
http://www.mytravelguide.com/city-guide/Europe-&-Russia/Italy/Rome/Taxis

Radio Taxi 3570
Radio taxi service in Rome.
http://www.3570.it/

Roman Homes
Tips on taking a taxi in Rome.
http://www.romanhomes.com/your_roman_vacation/transport.htm

Rome Matic
Search for taxi stands and operators all over Rome with the aid of this interactive map.
http://www.roma-o-matic.com/taxi_en.php3