Austin is my favorite town in Texas.  The nightlife on 6th and 4th street are unbelievable on a weekend.  6th street is a lot of fun with its blocks and blocks of bars lining the street.  4th is not as crazy and a little more tame but still a good time.  Some afternoon make sure you take the time to drive up into the hills and have some beers at Dry Creek, just remember to ALWAYS return your bottles;-)  Houston and Galveston are also a lot of fun with the deep-sea fishing and bars near Rice University like Ginger Man.