Have them pick up the weekly "In Dublin" guide or see the less complete online version here..

Trad is all over the place in Dublin, as are other sorts of wonderful music. It is one of the best music cities anywhere.

Try Hughes' at the back of the Four Courts.

O'Sheas.

Harcourt Hotel.

If it's singing they're after, there is the An Góilín singers club on Fridays these days I think. And last I heard, at Maye's pub.

Can't recall if they meet in summer, though.

If they lean towards a more enlightened sort of attitude, they might like to also have a look at Indymedia Ireland's what's on page for the arts.

Also, Temple Bar Music Centre, Bewley's on Grafton, Brazen Head, and one of my favorite places in all Dublin, Thomas Reads.