COTRAL (coaches in the Region of Lazio): http://www.cotralspa.it/ENG/linee_orari.asp
FERROVIE DELLO STATO (Italian railways): http://www.ferroviedellostato.it/

ROMA PASS - Cultural touristic card that costs only 25,00 € and is valid 3 days - IT INCLUDES A PASS FOR PUBLIC TRANSPORTATION

The official website of Italian railways can be found at: http://www.ferroviedellostato.it. There you can browse route options and timetables as well as purchase your train ticket! However, payments by credit card are not always successful! You may find yourself struggling with registration, credit card processing and eventually, failure.

A new payment option has been recently added to the site: now you can make your train ticket reservation without registering or using your credit card as you will be given the option (once in Italy) to make the payment in cash at one of the many shops in Italy that are connected with the SISAL network! (Most Tobacco shops).

You can also pay directly at train stations (cash or credit card), or at any ATM of UniCredit bank network (using your credit card).

To complete the payment (at the latest. 24h prior to time of departure of your train), you will only need the PNR code that is associated with your on-line reservation! At the moment, this seems to be the easiest way to go!