"Off on a slight tangent - I've sometimes thought that Beatboxing could work really well on some folk songs/tunes. Anyone know any examples?"

OK, this is one of the (very few) contemporary covers that they perform (rather than an old- time song) but here is the utterly wonderful Carolina Chocolate Drops, complete with beatboxing...

http://www.youtube.com/watch?v=wKTXJUYiAT4