This annual event, held on the last Sunday in September, features Leather, Bondage, Rubber and other Fetish and BDSM activities. Stretching over a mile you will find wall-to-wall dance clubs, bands, and booths where you can shop for a whip or learn about safe sex. It started out as an underground event to protest the gentrification of SoMa. It is organized by a non-profit to raise funds for many SF area charities. It's the third largest outdoor event in California. With a suggested donation is $5, it's quite a bargain today.