Walk off the Earth, They became famous for their guitar rendition of "Somebody that I used to know" by Gotye, but they do have a lot of their own stuff too. The girl in the band (Sara Blackwood) has her own stuff out too which I would recommend a listen.

Mumford and Son's. If you are into this type of feeling check out Phillip Phillips and Of Monsters and Men
If you are into a celtic vibe check out Great Big Sea. They have been around for a while but still tour and just released their 20th aniversary album.

Fun is another great band that is becoming more mainstream.