If you can survive the traffic-locked IH-35 corridor from Georgetown to Austin there a re a few places. We have two of my favorite brewers, across their product line, with Independence Brewing in south Austin
www.independencebrewing.com and Live Oak brewing right downtown
www.liveoakbrewing.com.
For in-house brewing try north downtown at the Draught House
http://beeradvocate.com/beer/profile/4858/?view=beerfly&sort=latest&start=10. One of my favorite brewpubs was the Bitter End which, after a fire and rent issues, eventually closed down. However, the master brewer moved down to a new barbeque restaurant near the river and is back to brewing killer beers at Uncle Billy's
www.unclebillysaustin.com. Try to make the special one-time kegs on the 1st Tuesday of each month.
If you like a place similar to Gordon Biersch, you might want to try NXNW (North by Northwest) in north Austin
www.nxnwbrew.com and ther's BJ's diwn in far southwest Austin.
Finally, you didn't asked about beer pubs but let me suggest at least two: The Flying Suacer
www.beerknurd.com and Opal Divine's
www.opaldivines.com (the atmosphere in the downtown location is great, I hang at the Penn Field south location, but I'd skip the north location). Note also that Opal Divines has proabbly the best single malt selection in Austin as well as vodka.
Slainte