I should think that the Liverpool Port Authority should be your first port of call for this type of information. I do not have a list for the whole of 2008, but I can let you know what to expect to see in July just to be going on with. 5th-Grand Princess, 10th-Black Prince, 11th-Saga Rose & Prinsendam, 20th-Crystal Sympahony, 23rd-Black Prince, 26th-Maasdam, 29th-Saga Rose & Grand Princess, 31st- Black Prince. This may not be the final complete list, but I hope that it will be of some help to you. Happy cruise ship watching.
Http://www.porttime.com/home.cfm will answer your question for any port in the world.