How about a chain reaction workshop? The idea would be for the leader to start off with any song at all, and then the floor would be open, but there would have to be some connection between each song and the one that preceded it. For example, the session could kick off with Missouri Borderland by Joe Newberry. The next song could be another song about bank robbing, or a song about Missouri, or about borders, or another song by Joe Newberry. The more abstruse the connection, the better.