I loved Sinead's rendition of "She Moves Through the Fair" in Michael Collins. Excellent example of matching music to the film.

Another I thought of: "Bamboozled" the Spike Lee film. Now, all those songs, AFAIK, were written by contemporary musicians, but I thought they were a freakin' brilliant scathing satire of the minstrel tradition.

And jumping around in time a bit, didn't the film "How Green Was My Valley" have some traditional music in it? As I think back on the era of melodramas like that, I also think of "Ryan's Daughter" which had traditional music, though I can't recall if there was any traditional songs in it.

Also, thinking of John Ford films, there was the beautifully crafted "The Dead" which had mostly drawing room music, and I'm wracking my brain now to recall if it had any traditional music or singing in it.

I do wish imdb.com included information on the film soundtracks. Does anyone know of a website that pays serious attention to the art of film scoring AND includes a database of films and their soundtracks?