Well all of those places are discussed at length in this section. And all of them are fairly easy to manage on your own (without a tour company). You can use the search feature of the forum to find information. Of course you can still use a guide if that is more comfortable for you, but do some reading and ask some questions and you will be better prepared for getting what you want out of your time there.
Carnival Cruise Lines:
Fantasy 90, Celebration 95, Victory 05, Conquest 05, Spirit 6/06, Freedom 6/08, Holiday 7/08, Victory 6/09, Valor 9/09, Dream 6/10, Splendor 8/10,Conquest 8/11,Magic 11/11,Triumph 4/12,Spirit 7/12,Freedom 11/12, Triumph 2/13 - The fire cruise
NCL Dream October 2006, RCCL Mariner OTS June 2007