Hi Redcrown,
The best international airport to fly into for Galveston in Hobby (HOU). It's about a 45-60 minute drive to the pier. I don't recommend Bush Intercontinental (IAH), it's about 2 hours. If you do fly Continental Airlines into IAH, you can fly their semi-reliable commuter to Ellington Field (EFD), just East of HOU and get a cab. It's about 45-60 minutes from EFD as well. EFD is just a small building on an airfield, not a full service airport like HOU.
(I have had the Contintental commuter cancelled twice. The airline then gives taxicab vouchers and sends you to the street to fight over taxicabs with your fellow passengers to get to the other airport.)
If you are flying your own private airplane or helicopter, you can land at Scholes Field, GLS. It's about a 10 minute drive from the pier.
Enjoy!