Barbara Shaw - regarding the key, it's traditional to pick the key based on what the voices you have can handle. Being an entirely vocal tradition, usually you don't pick a "key", per se, since it matters not a whit what it might come out to on an instrument, but the song leader (or group, by consensus) finds the tonic fa or la that makes it work for all the parts.

The part of the NPR program that I found particularly interesting was the traditional singers' discussion of their feelings about folkies using their tradition -- and the folkies feelings about it as well. (By folkies, I mean those who've come to shape note singing other than thru their church or community's tradition. Many (like me) are not in it for the religion, but for the music, though many also find the spirit comes through somehow anyway, though not necessarily as intended.)

~ Becky in Tucson