Jerry Willard's anthology entitled "50 Easy Irish Favorites for Classical Guitar" has an excellent arrangement of Danny Boy. In fact, I like it better than virtually every other arrangement I've heard, because Jerry doesn't bury the melody (*the* heart of this piece) under a mountain of blue notes and embellishments. It's in the key of D, so melody notes go as high as the F# on the 16th fret, yet it falls easily under the fingers.
IMO, it's as good as Steve Eckels's arrangement, and it's readily available. Finally, you get 49 other arrangements with it and downloadable audio!
I recommend it highly.