Traditional Irish Music

Wikipedia tells that that the folk music of Ireland (also known as Irish traditional music, Irish trad, Irish folk music, and other variants) is the generic term for music that has been created in various genres in Ireland.

In A History of Irish Music (1905), W. H. Grattan Flood wrote that, in Gaelic Ireland, there were at least ten instruments in general use. These were the cruit (a small harp) and clairseach (a bigger harp with typically 30 strings), the timpan (a small string instrument played with a bow or plectrum), the feadan (a fife), the buinne (an oboe or flute), the guthbuinne (a bassoon-type horn), the bennbuabhal and corn (hornpipes), the cuislenna (Irish war bagpipes, different from the Uilleann bagpipes, which was developed around the beginning of the 18th century), the stoc and sturgan (clarions or trumpets), and the cnamha (castanets). There is also evidence of the fiddle being used in the 8th century.  http://en.wikipedia.org/wiki/Traditional_Irish_Music

To learn about traditional Irish music, check “A History of Irish Music” (1905) by William H. Grattan Flood.
http://www.libraryireland.com/IrishMusic/Contents.php (Online book, can be downloaded or read in web format).

If you are interested in self-taught programs to learn of some of the traditional instruments, check ComhaltasLive, the weekly internet video programme of Irish traditional music produced by Comhaltas Ceoltóirí Éireann. These video-programs are organized by instrument, tune (reel, jig, etc.) and venue (competition, concert, etc.). 

Also, another source is the Revised Tunebook from the Kington, Harp of Tara Branch, of Comhaltas.