Another good website is :
Crociere 2012: offerte Costa Crociere, MSC Crociere 2012 nel Mediterraneo con Crocierissime.it.
Major cruise agency for Italy, apparently owned by the Costa family, based in Genova.
I have booked through them for an upcoming MSC cruise departing from an Italian port.
They have English speaking agents who will call you back.
Note that AMEX cards attract a surcharge. They accept PayPal but the exchange rate is awful with them, besides the vig charged. So, it's MC or VI unless you can pay in Euros.
They have specials not even listed on their website.