If you go a little out of the way, Lockhart Texas has the BEST BBQ in the state.
http://www.kreuzmarket.com/index.shtml
Lockhart is considered BBQ capital of Texas, with the oldest existing BBQ joint as well as the oldest BBQ joint owned by the same family. Kreuz Market is my opinion the best there.
If you wish to stay more in Austin (not much in Lockhart), County Line BBQ is where it's at. They have a location on a creek, as well as one on a hilltop overlooking the Hill Country.
If you go through D/FW, you can't go wrong in the Stockyards in Ft. Worth. They still have the cattle drives through the streets on weekends, though it's a bit touristy for me.
Houston I'm not as well up on, but I've heard great things about The Swinging Door.
http://www.swingingdoor.com
Have fun.