A massive (200,000+), diverse, and lively party, the Dyke March is not to be missed! Men are a substantial minority - as always, respect is advised.
The march itself starts in Dolores Park (after a lengthy rally/performance/party) and finishes in the Castro - recombining with the Pink Saturday brothers.
Website: http://thedykemarch.org/
Wikipedia: http://en.wikipedia.org/wiki/Dyke_March