There are quite a few in The Digital Tradition, a free 6800+ strong
database (many with tunes to play on your computer's speaker). It is available
from the website below, or mailto:digitrad@world.std.com for more information.
There is also a lot of other musical info and folk info on that ftp site.
http://www.mudcat.org/folksearch.html
Also, check out the Ceol section of
http://metalab.unc.edu/gaelic/gaelic.html
also try
http://www.geocities.com/CapeCanaveral/1690/lyrics.html