There is a singers session in "The Gables" pub on (I think) the last Sunday of each month. It starts around 9pm to 9:30. I shall get exact details for you in a day or two.
Irish Music Magazine has a session listing for the entire country and the Nenagh Singers Circle (http://www.geocities.com/broadway/alley/4749) web site has listings of many of the singers clubs (open to all comers). You will find a link to "Irish Music Magazine" on our "Links" web page.
Frank McGrath
Nenagh Singers Circle