I used SAS Shuttles on my last cruise. They were flawless. Apparently I'm too new to post links, but a quick Google of SAS Shuttles brings up their site.
SAS is the main provider. Depending upon how many people you have, a taxi or a rental car may be cheaper. Many rental cars are available in the terminal garage (if flying SWA Alamo is directly across the skyway over the drop-off lanes).