Super-easy to use and there are way more places around than you (well, I) ever suspected. It’s called BayAreaSpaces.org:
Search the most comprehensive free online rehearsal and performance space guide in the San Francisco Bay Area! BayAreaSpaces.org offers numerous search options that allow you to identify spaces according to size, cost, features, location and more. The directory includes spaces throughout 11 counties from Sonoma to Monterey….
Profiles include photos, detailed descriptions, dimensions, pricing info and many other features. An online map shows the geographic distribution of your search results, so you can find a space near you. Each profile includes contact information so you can easily get in touch with the right person for reserving the space. Now you can spend your time making art instead of worrying about rehearsal space.