This site has a lot of free Irish/folk tunes for any melody instrument. Also you might want to try tinwhistler.com. As for playing them, ornamentation and bowing are probably what most distinguish the Irish style (for ex. rolls, droning, cuts, trebling). A good book for
beginning Irish fiddle is A Complete Guide to Learning the Irish Fiddle, by Paul McNevin (at least, I liked it
). It is quite comprehensive when it comes to ornamentation and bowing, and has a nice collection of Irish trad. tunes.
Good luck!
