For BBQ, I like
1. The County Line
2. Rudy's
3. Salt Lick (all you can eat)
Also try some Tex-Mex. Chuy's or Hula Hut is very good.
Sight seeing:
1. UT
2. MT. Bonnell
3. Lake Travis
here's some info for visitors:
http://sun-design.com/austin/
BTW, if you like strip clubs Austin has some nice ones such as the Yellow Rose or Sugar's.