About.com
Tips on getting from Fiumicino Airport to Rome. The page includes a link to a timetable detailing the train service between the airport and Termini train station.
http://goeurope.about.com/cs/romehotels1/a/rome_transport.htm

Easyjet
Advice on getting to Rome from Ciampino Airport.
http://easyjetinflight.com/destinations/2004/Rome/index.html

Enjoy Rome
Includes timetables for train services from Termini station to Fiumicino.
http://www.enjoyrome.com/tourist/cityguide/getting.to.and.from.the.ci.html

The Church of Santa Susanna
Basic information about public transport in Rome including airport trains.
http://www.santasusanna.org/visitorInfo/transport.html

Travel Italy
Covers the basics of travelling between Rome and Leonardo Da Vinci International Airport (Fiumicino) by public or private transport.
http://www.travel.it/roma/romefiu.htm