Sutro Project / Folsom Street Fair
As the world's largest S&M/leather event (and California's 3rd largest spectator event overall with 400,000 attendees), the Folsom Street Fair is beyond the imagination of most who haven't been. Most of SOMA is closed to traffic and jam-packed with people. Organizationally, it is a model for other Street Fairs in San Francisco.
There's plenty to check out: live music, dancing, "toys" for sale, "play", etc. As a tourist, participant, or both - the event is most remarkable for it's astounding variety of sexual expression.
There are food and beverages available for sale, be sure to stay hydrated in the crowds.
Website: http://folsomstreetfair.org/
Wikipedia: http://en.wikipedia.org/wiki/Folsom_Street_Fair
