Keep in mind, however, that just because they're there, doesn't mean you can use them. Generally speaking the laundry facilities are closed while you're in port. That's because of environmental regulations in port, generally. So you have to be careful about the timing of washing your clothes. The ships close the laundries at about 10 or 11, depending on the ship, and so you may only have from 6 to 10 to wash and dry your clothing.
On most of the ships the laundries also have ironing facilities. My wife and I take along:
soap powder (in baggies)
Dryer sheets (also in baggies)
Spray starch (we usually leave the can on ship)
The facilities come in very handy if you get your clothing ironed early on formal nights. It is very helpful.