If you google 'ports of call cruise boards' the first link should take you to a most excellent site full of info.
How about all of them, or you could go ashore and get them all half price from the local companies, bearing in mind the ships tours are run by local companies, but they put a 100% mark up on them, believe me, im talking from experience. you can even get buses with other cruise passengers and share the total cost.
This is a decision you have to make yourself. We have no idea whether you are active or sedentary, what you like doing, seeing or where your interests lie. Do your homework and read about what is on offer from the ship then look at the ports of call tourist sites on the net and make a decision as to what suits you and if you are adventurous do it yourself. I know that you will get people saying "be sure you don't miss the ship" but you aren't going to are you because you will allow enough time. Regards. ... Neil.