Another vote for 21st Amendment. Also add Magnolia Pub on Haight Street to your list
http://www.magnoliapub.com/index.html
There are a few garage breweries in SF, some get to sell their wares at 21st. I hesitate to post names/links given that most operate in a hazy legality. Google is your friend.
Also, as mentiond above, there are a ton of bars that serve local and regional beers: Zeitgeist, Pi, Rosemunde, Toronado would be the ones where you'd find me