Hi Jettagirl!
I asked around on another board about this as well! I am going on a week long southern caribbean cruise.
I am bringing four or so sundresses (cotton/rayon/silk), several skort style skirts/shorts, regular shorts, as well as several just-above-the-knee summer skirts.
I wear a lot of sport-tanks. Nike makes some nice tanks which you can work-out in, they have a built in bra and come in an array of GORGEOUS colors. I have about half a dozen of them in different bright colors - I plan to pair them with my skirts/skorts/shorts for days on the ship, and for shore excursions.
I am also bringing a lightweight crinkly cotton white cover-up shirt (just a very lightweight button up, long sleeve shirt), to wear on the islands over my tanks, it will help to dress-up tanks a little, and protect my fair skin from the sun.
The sundresses are for dinners - as is the gown I am bringing. 
Hope I could help! I have been obsessing about my clothes as well! hee hee
