The City and County of San Francisco has a new open data site:
Please follow the link to the site to search, browse and view San Francisco data.

Description: 2076 dataset for the City & County of SF
Agency Name: US Census Bureau
Date Released: 2010
Time Period: Snapshot
Frequency: Every decade
Location of dataset:
Format: CSV
Location of Data Dictionary:
Additional Details: Type in "San Francisco County, California" or "San Francisco city, California" in the Geography field

DataSF is a clearinghouse of datasets available from the City & County of San Francisco. Our goal in releasing this site is:
(1) improve access to data
(2) help our community create innovative apps
(3) understand what datasets you'd like to see
(4) get feedback on the quality of our datasets.