Now a centroid of night clubs and home to the Folsom Street Fair, SOMA's historical edginess is rooted in the 1970s with a migration of sexually-liberated (primarily gay) folks from the Haight-Ashbury district. The devastation of the AIDS virus and the rise of tech-culture in San Francisco has diverted, if not lessened, the intensity of the area.
Adjoining the Civic Center, Downtown, South Beach and Potrero Hill, the "neighborhood" is large, industrial, loosely-defined and best experienced with a game plan.
11th st and Folsom is the main center of clubbing activity, but 1015 Folsom (SF's biggest and most famous night club) and the Endup are towards Downtown off 6th St. Also towards Downtown is Yerba Buena Gardens and its great museums - including MOMA, Zeum and the Contemporary Jewish Museum.
Wikipedia: http://en.wikipedia.org/wiki/South_of_Market
