Can vouch for Lunenburg and the Bluegrass festivals in particular. There are open mikes usually at the BG festivals, and great field pickin'. They're all good. I will be attending for sure the Bluegrass festival in Stewiacke Labour Day weekend. It is by far the most laid back of the events I've attended - kids and dogs welcome, multitudes of RVs and campers, it is on the river, grassy site, very relaxed atmosphere (gets more relaxed as the night goes on), tons of talent. But you will likely enjoy any of the events George has listed. ;-)