A few usefull links to help you plan your cruise (make reservations, read reviews and tips, talks to other cruisers and also see the ship thanks to on-board webcams and have a preview of your next destination):

http://www.expedia.com: To find cruise deals, make reservations and read reviews.

http://www.kroooz-cams.com: A great place where onboard webcams are all repertoriated, there is also a nifty port-of-calls webcams, links to the different companies and a forum section where fellow "krooozers" can share their informations.

http://www.cruisecritic.com: As the name mentions, a place to read cruise reviews.

http://www.cruise-addicts.com: Read reviews, write in the forum and browse the extensive photo albums section for a look at the ships, cabins, destinations, etc.

http://www.cruisemates.com:Find bargains, read reviews and tips, chat with fellow cruisers.