As far as Irish music goes, I'd like to add that some of the best music is coming from Stateside.

Try Solas & Liz Carroll. For Ireland, I'd add Deanta. And don't forget England and Mike McGoldrick.

And where is your cut off for "young" exactly? It seems to me some of the acts listed above (Battlefield Band, Capercaillie) would most definitely be at the upper end of the young scale!