Dan Must be sure to be more careful where I sit in future, at the Goilin!
Gearoid
If its instrumental music you're interested in, the best starting point is probably Hughes's of Chancery Street. Its beside the Four Courts - the main court complex in Dublin, a few bridges upriver from the city centre. There's a session every night (sometimes with a second in the "snug") - and the standard is very good. Also a good place to ask about other sessions - its rotten with musicians, dancers and singers.
p.s. All this at night, incidentally. During the day the clientele is mainly lawyers and criminals (no cracks about tautology, please).