The Galveston Railroad Museum was fun, though part of it was still under construction. Hurricane Ike did a lot of damage back in 2008, and it's taken them a long time to restore everything. It was an interesting field trip, and we'll probably go again next school year, when the model train area has reopened. As it was, the kids had a great time exploring the old train cars, and climbing on a couple different engines.
Of course, you can't go to Galveston and not go to the beach!