Well I didn't reply because I rarely read Off Topic. I only came here to post another cool song. This is quite a nice song, called Song of the Lonely Mountain by Neil Flinn, apparently its the End Credits song.
http://www.youtube.com/watch?v=tqnSoTgjBrg
Back to the OP, Peter Hollins is a great singer though sadly I only like his covers of fantasy songs or themes such as The Hobbit or Skyrim (I'm not a fan of contemporary or pop music). He sometimes partners with another great YT star called Lindsey Stirling who combines contemporary violin music with dance for her music videos (in amazing backdrop locations, like a desert, mountain, castle, forest and an epic ice sculpture somewhere in north Europe IIRC. She was actually on Britains Got Talen but lost out, if you can believe that
). Check out Peter Hollins and Lindsey Stirlin's music video of the Skyrim theme.
http://www.youtube.com/watch?v=mgPienNLSyk
Peter sings (in the ancient Nordic language no less), Lindsey dances and plays the violin, and they both duel using magical fireballs and musical instruments.
They also did a version of Game of Thrones.
http://www.youtube.com/watch?v=rUgAgfO-16s
Lindsey plays Daenarys Targaryen, Peter plays Jorah Mormont I think (not really sure).
Loreena McKennit is also a really good Irish (IIRC) folk singer. Check out her song "The Old Ways". It wasn't written about the Game of Thrones/Song of Ice and Fire, but fits it perfectly.
http://www.youtube.com/watch?v=-4PC451UEhU