If you want the traditional vernacular stuff I dare not name, then Bonnie Shaljean has the right format: "everybody sat in a big circle and each person would sing or play one thing in turn, and when it came to the guest they'd do two or three numbers, and it just kept moving around the ring." Also her requirement that everyone sings from memory is a good idea. Firstly, it removes those homogenized versions of songs found in certain books, and stifles unsuccessful attempts to duplicate well-known singers; e.g. Carter Family, Burl Ives, Joan Baez. Secondly, if you are singing a traditional song and are part of that tradition, then of course you sing the song from memory, because you have been singing it from memory for decades.