Genesis House: 33 Turk Street, San Francisco, CA 94102, Phone: (415) 861-2749 is an option if you're looking for a community-oriented space.
The Mill: 500 Van Ness Avenue, San Francisco, CA 94102, Phone: (415) 346-9999 is a larger coworking space with with amenities like meeting rooms, private offices, and a communal cafe. It's a good option if you're looking for a more traditional coworking space.