country groups:
1) The Chieftains and Earl Scruggs:
http://youtube.com/watch?v=ByYSkRGrMqw2) Emmylou Harris and Ricky Skaggs:
http://youtube.com/watch?v=Q5BMiXfpG4Q3) Cherryholmes:
http://youtube.com/watch?v=e7LzqvN2M5A4) Alison Krauss and Union Station:
http://youtube.com/watch?v=GT0QFM78fpo5) Here is Alison with the Chieftains:
http://youtube.com/watch?v=xOpY0wQdJ5w(Some of her bandmembers were featured doing "I am a Man of Constant Sorrows" on the 'O Brother, Where Art Thou' soundtrack:
http://youtube.com/watch?v=waUpZ27nYAY ) That whole soundtrack is amazing.
6) Del McCoury and the Chieftains:
http://youtube.com/watch?v=F3Is_C5KIVs7) The Duhks:
http://youtube.com/watch?v=VYdk_TcCeW8Now, am I missing any other amazing things out there?!