I do like most of the pieces mentioned here (especially Pachabel’s D Canon), but I hope it isn’t too lowbrow to admit that I love Amazing Grace.
Siege, I totally forgot about Ashes! That’s easily near the top of my pile…gorgeous song to play on guitar, too.
Yet another atheist with a thing for religious music (definately the best thing to come out of christianity). I’m always interested in picking up more and have got some ideas from other contributers, thanks folks.
I’ll mention two pieces here that work for me in different ways.
Mozart’s Great Mass in C minor
This just about epitomises the grandeur of the ‘high church’ mode of worship. It is in the most literal sense of the word an awesome piece of music. In listening to it I am reminded of how I feel awe at the universe in general and how similar this must be to how religious people feel about their god or gods.
Duruflé’s Requiem
Chosen as a deliberate contrast to the above (the god of Mozart seems to me to be above most human concerns) it seems to me this speaks about a more personal relationship with god and (more importantly for me) about the acceptance of death as an inevitability not to be feared. Contrasting this requiem, and the Faure mentioned above with the more well known requiems of Verdi and Mozart is quite interesting, the messages about the nature of god appear to be almost completely contradictory.
John Rutter has been mentioned. For specific anthems by contemporary writers, his “For the Beauty of the Earth” is wonderful.
One of the advantages of beeing a Lutheran is listening to all that wonderful JS Bach music on a pipe organ. I know, other denominations play Bach, too, but it’s a Lutheran tradition.
I also like a lot of Mozart’s stuff, but being another musical philistine, I don’t usually know what’s sacred vs. profane with him 
As far as individual hymns, favorites include A Mighty Fortress, and Joyful Joyful We Adore You. I’m sort of ambivalent about Amazing Grace; it can be wonderfully performed on bagpipes, but it’s so easily screwed up on bagpipes, too.
Here’s a weird one: O fell in love with O Holy Night watching Home Alone. Remeber the scene where Kevin goes into the church, and sees the Evil Neighbor watching his granddaughter’s choir practice? That choir they used kicked ass singing that hymn, and it’s been a favorite ever since.
Another vote for Allegri’s Miserere.
Fascinating story behind this piece: it was written for use in religious services, and one particular pope was so impressed that “the work thereafter was protected and a prohibition was placed on its use outside the Sistine Chapel at the appointed time”. And so it stayed for 200 years until a young lad called Wolfgang Amadeus Mozart: “As with any tourist, [Mozart and Emporor Leopold] visited St. Peter’s to celebrate the Wednesday Tenebrae and to hear the famous Miserere sung at the Sistine Chapel. Upon arriving at their lodging that evening, Mozart sat down and wrote out from memory the entire piece. On Good Friday, he returned, with his manuscript rolled up in his hat, to hear the piece again and make a few minor corrections.”
I love this story.
until a young lad called Wolfgang Amadeus Mozart arrived on the scene:
:smack:
Many of these are going to be fairly obscure chants…
Machaut, Messe de Notre Dame
Ockeghem, Requiem
Palestrina, Magnificat, in the first tone
“Alleluia: Pascha Nostrum”, sung to the Old Roman chant melody; Ensemble Organum’s recording of this may be my favorite piece of music ever
“The Noble Joseph”, sung to the Bulgarian chant melody
Mozart, Requiem
“Holy God, We Praise Thy Name”
The Russian Lenten melody for the Litanies
The podoben “Hearken, ye women”
I’m not sure how well the “religious” theme stands up for this one, but it sounds “sacred” to me. The translation of the lyrics sound somewhat religious in nature, as well, so I’ll list it here.
Dead Can Dance “Song of the Sybil”, particularly the live version on Toward the Within. It’s a traditional 16th century Catalan piece that is beautifully performed.
I have a terrible knowledge of the music I like so I can’t be as detailed as the other answers in this thread, but I basically like most classical pieces and a couple of more modern tracks that I like have religious undertones.
I like a group called Enigma, and my utter lack of complete knowledge mentioned above means I am not sure if it should be considered religious, or just religious sounding or parodying.
I also heard a song on the OC (tv drama) that was a religious song.
I sang the Beethoven Mass in C over ten years ago, and I can still recall every note of the bass/baritone line – which is pretty unusual for me, as I don’t have a good memory for fugal sections.
Best of luck on your upcoming performance!
I don’t understand why Amazing Grace would be considered “lowbrow.” It’s a lovely song, and one I should have included in my favorites.
Well, it’s not high-brow, long-hair music (:)) but I’ve always loved Ferlin Husky’s On the Wings of a Dove. Great old timey country gospel. And, when I worked at a music store, I got a promo of the Andy Griffith album, I Love to Tell the Story: 25 Timeless Hymns and I actual find myself listening to it quite a lot. I’m not religious in the slightest and don’t consider myself a Christian but I do enjoy the old hymns…
Hildegarde von Bingen’s works are lovely to put on in the background while you’re reading or praying.
My favourite Hymn is “Be Thou My Vision”, sung to the tune Slane. I love the words, and the tune is quintessentially Irish, and stirring.
The Lyrics are here:
http://junior.apk.net/~bmames/ht0112_.htm
I like the big, belting hymns that have great chorus and sound best sung by a choir. “Guide Me Oh Thou Great Jehovah”, “Oh For A Thousand Tongues To Sing”, “As I Survey The Wondrous Cross” and “How Great Thou Art”.
If Spirituals count, you’ve got to rate Nina Simone’s “Sinnerman” way up there.
Leos Janacek’s 1926 Glagolitic Mass, an enormous hurlyburly of dramatic choruses, surging orchestration, and howling organ solos.
Kenneth Anger used it as the soundtrack of his 1954 underground film Inauguration of the Pleasure Dome, which I first saw in 1982, under decidedly secular circumstances.
Forgot to include a link to The Cyber Hymnal
“Swing Low, Sweet Chariot.” The best rendition that I have been able to find thus far has been by Beyonce.
“A Mighty Fortress Is Our God” is one of my favorites. The best recording I have found thus far is by the Promise Keepers.
WRS
I’m singing the Allegri Miserere in about seven hours from now… I sure hope our principal treble is up to it, it’s a long way upstairs to them high Cs. All I have to worry about is a nice deep bass line with plenty of low Fs 
O Come O Come Emmanuel – especially the earlier versions and harmonizations (like medieval / Renaissance era).