I really got a lot of info from www.portreviews.com
Also, i looked up each islands "official" website to find out what there was to do as well.
If you have some time, there are lots of books out there about Caribbean ports of call.
We are going on the Mariner on Feb 15 and we still need to decide if we are going to buy RC's shore excursions or go it alone!
Life is for the living