I believe Princess has tham on their ships, and Royal CAribbean has a few as well, not sure about the Carnival ships with them. Like the previous poster mentioned, go to the cruiseline web-site and look for their web cams, quite interesting.
Check out the Fleet pages on Carnival's website. If the ship has webcam there will be a link on the right side of the page.
A Bad Day At Sea [with power] Always Beats A Good Day At Work
Carnival: Glory 2004, Destiny 2008, Splendor 2009, Freedom 2011, Valor 2012, Dream 2013
Celebrity: Summit 2011
Princess: Ruby 2010, 2014, Caribbean 2013, Coral 2014