Originally Posted by
ShopAround
http://www.romashuttle.com/
I've used them for city/airport transfers; you can book in advance online. Looks like the Civitavecchia-Rome shuttle is 130 euros for three people, which is more than the train (but less than what the cruise line charges), but it's door to door.
I used
Airport Shuttle last time and they offered a good service for a reasonable price. You may what to have a look on thier website as well. They are pretty fast with a reply per email if you have any questions.
Cheers
totti