Queer Contra Dance is a "friendly, folksy venue for queers and friends to meet and contra dance." More information about contra dance here. They have weekly dances usually at the Lake Merritt Dance Center on Saturdays that are $10-$15 sliding scale and accept whatever payment you can afford. There are lessons before the dance for beginners.
External Link: http://www.lcfd.org/sf/index.html
Oakland Local story on Queer Contra Dance.