If you are interested in a nice drive out to the famous Hill Country of Texas I would suggest going out to Fredericksburg to spend an afternoon touring the Pacific War Museum. The new exhibit space opened in 2009.
I finally got the chance to go there last Sunday and came away mightily impressed!
LBJ's homestead is out here as well if you are into that kind of thing. His library is near DT Austin.
If you get to Austin visit Waterloo Records for some good tunes and dine at Wink Restaurant. You won't regret either! Just bring some $$$ because the food is great and the music is awesome.