The cruise threads have excellent tips on packing lists. The only items we didn't use were the duct tape and crazy glue. I read all the FAQS on the Carnival web site and it was useful to know that shampoo, body wash and toothpaste are provided. If you run out, just ask your cabin steward. They also had one use samples of shampoo & conditioner, in addition to the shampoo dispensor on the wall. The cabin also had a hair dryer built into the dresser drawer.
Bungee cords are a great way to keep your towels from blowing off deck chairs. Sports bottles are useful for walking around the ship and day excursions. We filled small cups with ice and then dumped them into our sports bottles. We opted not to pay $50 for a soda card. The ship had iced tea, punch and lemonade all day. I also brought powdered packets of flavored drinks to add to our water bottles.
I sent a Romace package to the room. That gave us each a T-shirt, a visor, one towel, a bottle of champagne, $15 in photo coupons and 4 drink coupons.
Having a small backpack or beach bag for day excursions is really handy. I also brought a waterproof case that I could put my sign & sail card, a credit card & cash while on the beach or at the pool. If you are going to use the cabin safe, bring an extra credit card or the card you use at your grocery store to swipe/lock the safe.
The medical room on board has a large supply of bandaids, first aid cream, aspirin, Tylenol, seasick pills and Alka-Seltzer for free.
You can request a deck of cards at the Purser's desk.
Bring a sweater or light jacket for the theater and casino. It gets chillly.
Have fun!
-D