It often depends on my mood. However, I've always liked Stan Rogers, Archie Fisher, Chris Foster, Nic Jones, and Maddy Prior. Pam Morgan and Anita Best from Newfoundland are also pretty good.
Recently I've discovered Kate Rusby, a fine singer barely in her twenties who comes from the same part of the world as my paternal grandfather. I've purchased Hourglass, and just today ordered some of her other CD's which are not available in Canada. She seems to have never toured North America, and I am told that one of the reasons is that she has a fear of flying. I'd love to see her in a place like The Ark in Ann Arbor, Michigan.
Of the old timers, A. L. Lloyd, Ewan McCall, Woody Guthrie, and Leadbelly.
Of bands there are too many to list.