The popular free Broadway Shuttle (the "B") has been extended to operate Friday and Saturday nights. The evening (blue) route differs slightly from the daytime (orange) route, stopping in front of the Fox Theater and running a few blocks further north to serve additional restaurants and bars in the area.
News of the service: eastbayexpress.com/92510/archives/2011/06/22…
Map, schedule, and other information: http://www.meetdowntownoak.com/shuttle.php
The shuttle makes it much easier for visitors and residents alike to enjoy the nightlife in Jack London Square and Uptown without having to walk to/from nearby BART stations.