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: Location and count of trees by block where DPW has a tree maintenance agreement.
Agency Name: Department of Public Works - Bureau of Urban Forestry
Frequency: Daily
Location of dataset:
Format: CSV
Location of Data Dictionary: N/A

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.