A word of caution, essential items that you forget may have to be purchased on the ship or on an island. A couple of examples -a tube of toothpaste on the ship cost about $4, a cheap plastic comb on a Carribean island cost a dollar. Not really big expenditures but you might be able to get them a bit cheaper at home and have more fun dollars for cruise activities.
Make sure you read the thread on how much money to take on cruise. Valuable inputs from Cruisemate members are in this thread.