For San Francisco all the crime data is published (well, other than some sensitive data like the locations of rapes). datasf.org has a listing of all the geospatial data available for SF. A lot of other cities have their own data repositories. Washington DC has one of the best (http://data.dc.gov/) and New York has a good catalog as well (http://www.nyc.gov/html/datamine/html/data/data.shtml).