I doodled with this once using different sites and I came out with the following as plausible.
Ithaca, New York
Madison, Wisconsin (Green Party members on the city council, strong opposition to an amendment against same-sex marriage)
Minneapolis-St. Paul, Minnesota
Portland (Oregon's or Maine's.)
Santa Cruz, California (Also in the Bay Area, but maybe somewhat independent to SF)
San Francisco, California
Seattle, Washington (Strongly approved Referendum 71 in favor of same-sex unions, highly secular)
For smaller, or possibly smaller, places
Asheville, North Carolina - Reportedly quite a liberal college town for the South. Also Carrboro.
Burlington, Vermont - Progressive Party has the mayoralty and some of the city council. The Vermont Progressive Party does appear to be genuinely progressive.
Key West, Florida - Maybe not that progressive, but one of the first places to have a gay mayor.
Marfa, Texas - Well sort-of. It did have a Green Party mayor and like a minimalist art museum or something.
Telluride, Colorado - Its county strongly supported civil unions and medical marijuana while strongly opposing a ban on same-sex marriage.
According to Gallup Vermont is the state with the highest percent as self-described liberals while Hawaii has the lowest percent be self-described conservatives. Massachusetts and New York also look to be relatively high in both self-described liberals and Democrats. DC is the only place they list as net-liberal, more self-described liberals than self-described conservatives, but is not a state.