I have to agree with Garmorn about Kings Hobby. The new management has really taken a dislike to rpgs/gamers, and its beginning to show. I suspect they'll eventually phase out everything that can't be had at a Hobby Lobby. Besides, Kings Hobby doesn't support a gamer registry, nor does it have a bulletin board to post ads upon.
Other, lesser known shops exist as well: there's one on the lower level of the Dobie Mall off Guadalupe, and there's Thor's Hammer out on 183 N, both of which are friendlier to gamers.
There used to be a monthly Game Day that occured in a school gymnasium near Highland Mall. The SCA meets weekly in Walnut Creek's parkland area - some of them are table-top gamers.
Regarding, sjohn's Yahoo! group: his isn't the only one with an Austin, TX based membership! Do a search. I left the former after I discovered it was completely undiscriminating (meaning that persons were using the forum to encourage drug use and other illegal activities under the pretext of gaming). As long as it had a "d20" or "RPG" mention, one could advertise anything... just a head's up, if you have any younger gamers in your family.
Bad DM