About contra dancing:

The history of American contra dance

Other dance communities in California and Nevada:

Sacramento Country Dance Society

North Bay Country Dance Society

Traditional Dancers of Santa Cruz

Monterey Country Dance Community

Bay Area Country Dance Society

Sierra Contra Dance Society (Reno & Carson City, Nevada)

Contra dancing nationwide:

Country Dance and Song Society

Kiran Wagle's excellent index of contra dance groups nationwide

Greg Scragg's The Dance Gypsy, which features a very cool search engine that locates dances by date, dance style, and geographic area

Charlie Seelig's incredibly comprehensive listing of everything you can think of related to contradancing in the US and around the world, including festivals, weekends, regular dances, bands, and callers