Key West is a nice port to walk around and ship, pick up some key lime drink/pie, etc. There are some places that are interesting, I know there is a butterfly farm near by.. Best bet is to go through all the excursions offered by your cruise line and see what looks good to you....some you can just do on your own, others better to book through the ship.
Thanks for your response. I did the on and off trolley and stopped at a nice natural beach and the Hemingway house. I loved the architecture in the historic area and would love to "winter" down there one year. (When I've won the lottery and can "Winter" somewhere!)