Sad to relate that "The Lighthouse" no longer exists as a Pub in Howth. You might get a session in the Pier House in Howth on a Sunday, but I'm not too sure about that. Howth is well worth a visit, but locations for sessions are dissapearing fast. The one session I'm sure of is the singing circle on the first Thursday of the month. Nowadays its held in the Sea Angling club on the pier nearest the Dart station.

As far as I know Hughes still has sessions 7 nights a week. Cobblestone is usually worth a visit also. Both are accessible via Luas (tram) from Connolly Station.

Temple Bar, as has been said, is a bit of a tourist trap, but its probably the best place to find a tune during the day in the City Centre apart from the Cobble Stone at week-ends.