If you ever get to Southern Ireland and visit Kilkenny, there's a Monday night session open to reasonably good amateurs at Cleere's Bar near the centre, been running for over 30 years now. It's had various members of The Dubliners pop in, Christy Moore, individual Clancy Bros and others just drop in, but it's 90% pure ameteurs, one of the great open mic sessions, oh and I'm there on June 12th ;)