Carnival uses the Mears Bus company as its method of transportation to Port Canaveral. The cost is $15 one way, $30 round trip. You can purchase these tickets right at the airport from one of the Carnival representatives. They will be waiting around the baggage claim area, holding a Carnival sign, and will direct you to the busses. If you don't see these people, Mears also has a ticket booth in this area as well. The busses are modern motorcoach-type and are very nice. We used them earlier this month for our cruise on the Pride. The trip is almost an hour, so they provided a movie during the ride. If you prefer a limo/towncar type method of transportation, I recommend the Tiffany Towncar Service (www.tiffanytowncar.com
). This way is considerably more expensive, but it is a very nice and well-run company. We used them for our Disney trip this past summer, and we did inquire about using them for a cruise. I don't remember the actual cost, but I believe it was over $100 for a round-trip ride. They will email you a quote if you inquire with them. (ask for Moe, he's great!)
Hope this helps!