OK, maybe not my absolute favorite kind of music, but there are big (?) fans of this sort of thing.
There is a company called Columbus Washboard Company that can supply you with all your Washboard playing needs. They even have a page with links to mp3 tracks of washboard music. They also have a helpful list on how to use your washboard to actually wash your clothes.
[A note: the first item on the aforementioned list states: "It is okay to wash laundry in cold water." When you use Google Language Tools to translate this into French and then back into English it comes out as, "It is okay to wash laundry in cold toilets." Actually, that is not such a good idea. Except maybe in France?]