Then there's the grange hall. Most rural communities in the US have an old grange hall, and many have been restored and are used for folk music and dancing. Just put "grange hall folk music" into google and you'll find many of those. They're usually small wooden buildings with fantastic acoustics (no sound system necessary) and a great community feeling.

Across from Seattle on Bainbridge Island is a great grange hall venue hosting the Seabold Second Saturday Open Mic (no mic). A great venue - only problem, for us mainlanders we have to leave early to catch the ferry back home, and it's so popular you enter a lottery and may or may not get to play that evening.

Cheers, S, in Seattle