Thirsty Bear features many beers on tap all the time.  They have a list of regular beers and specialty/seasonal beers.  They do a pretty good job of explaining all the beers they have, so check their site for all the different beers.

Beers tend to be more on the lighter side than some San Francisco breweries.  But they cater very well to the convention/after work crowd.

A cask conditioned beer is put on the hand pump every Tuesday night at 6pm.  Only one goes on a week, so Tuesday is the day to go if you want a cask beer.

All beers are served in 20oz. glasses for $4.00.