Sports Basement has 5 locations now, 3 of them right here in San Francisco.
The newest recently opened in the heart of downtown located at the corner of 5th +Market street. It took us by surprise a few weeks ago while taking a post-coffee short walk from the Mint plaza, the main entrance is on 5th street side. This is a temporary pop-up style store, it will shut down shortly after the 2012 Holiday/End of year season.
They have a blog for each location with plenty of product/activities information as well as community events [basement buzz]. There's also bike repair services, with mechanic in/out update displayed on the window.
The window picture below is taken from the Market street side, the train did some perfect timing there :)