This part of the Northern Journey website should give you a good start, middle, and finish to your search:

http://www.northernjourney.com/cdnfolk/res/canfolkres.html

Things that pop into mind include the Borealis festivities happening in Toronto, starting on the last weekend of June, (June 29th I believe)...as well as folk festivals such as Mariposa and Home County. Enjoy!

~b.w.