This kinda leaves a lot of room for pretty any much musical style. Here are a couple lesser known commodities in very different genres I am a huge fan of.
Floater (
http://www.floater.com/) - Local Oregon rock/alternative group. They have an enormous fan base up here and have already turned their heads at a larger contract with a major label in order to do the music the way they want. They have a distinct sound and all their albums are quite different from each other. Plus, they put on one heck of a live show. Very talented musicians who have fans that are more dedicated than a lot of mainstream artists out there!
Julie Fowlis
http://www.juliefowlis.com. Traditional Scottish gaelic folk singer who is considered one of the best scots-gaelic singers out there (next to karen matheson). Its a little-known language that is overshadowed by its irish language counterpart. She is quite good at the whistle and bagpipes also.
Another artist I always recommend... who has had some popularity, but never really reached the mainstream audience that much is Loreena McKennitt. Her music defies any one music category although her later albums have a more Mediterranean flavor and her earlier works are primarily celtic. Beautiful voice and she tends to have a ridiculous amount of world instruments for each song. I've met very few people who did not fall in love with her stuff. (and no... she is nothing like enya)
