I get the feeling that there is a lot of useful material for Irish on the Internet, even Old Irish, but it is poorly indexed. I have found some resources which fascinate me.
The 1890 Kuno Meyer edition of The Voyage of Bran, my favourite of all Irish mythological stories, is available with the Old Irish text and English translation along with Alfred Nutt’s companion volume of criticism. Meyer’s Irish Metrics can be found online in a perfect demonstration of how not to digitize a book.
The Old Irish text of the Aided Froích (“The Death of Fróech”) edited by John Strachan in 1903 is helpfully presented with all grammatical forms explicated. The Timeline of the Irish Language found on this site is quite interesting.
I am fortunate enough to have two classmates who are native speakers of Irish, and think that I shall get started on the modern language with the hopes of more efficiently learning the Old and Middle forms of Irish.