The Missa Solmnis isn't a bad place to start as far as choral works are concerned. There's a ton of very cool a capella stuff out there, though. I strongly recommend looking into Frank Martin's "Mass for Double Choir". In fact, just let me know and I'll make a copy of it available to you.
Sunday, April 01, 2001
Josh responds: "I'll try, Dan, but I can't promise much. I don't like vocal music, so I don't own much - off the top of my head, I think all I've got is: the Missa Solemnis, a Vespers and a Mass by Rachmaninov, Mahler's fourth and eighth symphonies, Beethoven's ninth, Anonymous 4 doing Hildegard von Bingen's chants for the Feast of 11000 Virgins, Debussy's "Pelleas et Mellisande", and some Brahms settings of love songs from some era or another."