A couple of years ago I got fascinated with the national anthems of the Celtic peoples. I missed St. David's Day for the Welsh, and I'll try to get to it soon. But here, in honor of St. Patrick's Day is the Irish National Anthem, in several versions.
First
http://www.youtube.com/watch?v=4pHO7GW0MKEdespite what it says about never singing it in English, the words were first written in English and later translated into Irish.
Here it is in English
http://www.youtube.com/watch?v=_OyX3DHYtkY&NR=1 A complete version, followed by instrumental renditions
http://www.youtube.com/watch?v=_OyX3DHYtkY&NR=1 The wiki article, including a complete translation
http://en.wikipedia.org/wiki/Amhrán_na_bhFiann You can also hear it being sung at sporting events on some of the related videos on YouTube
Happy St. Patrick's Day!
Edited to give correct url for wiki article. Thanks to TRiG for pointing out error in original post.