Finding good choir music that is appropriate for your choir's skill level can require a little bit of research. Some websites are more user-friendly than others. Jackman Music (www.jackman.com) often has audio samples of choral pieces. Sheet Music Plus (www.sheetmusicplus.com) will often have a preview of part of the score and/or an audio sample available. LDS Music Source (www.ldsmusicsource.com) is very user-friendly, with an audio sample and a full preview copy of the score available for every piece that they sell. Sally Deford's music website (www.defordmusic.com) also has audio samples for most of her composistions. Choirworks (www.choirworks.com) has a practice mp3 for each piece as well as a pdf preview of part of each piece.
Here is a list of some resources that you may want to consider using:
Experience
Start with pieces that you have sung in choir and enjoyed. Whenever I sing a piece in choir that I really like, I write down the title and composer/arranger or buy a copy of it, so I can find it again if I ever need it.
Ask Around
Ask other choir directors, people
who have been choir director before, or choir members who have sung for a while what
their favorite pieces are. Choir is a lot more fun if you sing good music that people like to sing.
The Choirbook:
Most wards have copies of The Choirbook sitting around somewhere. Even if you don't, they are extremely inexpensive: $2-3 per copy. There are lots of very good pieces and arrangements found inside, so do some exploring.
Stake/Ward Music Libraries:
Yes, I know that in many stakes, this is one of those mythical, pot-of-gold-at-the-end-of-the-rainbow things: everybody thinks it might exist, but nobody's actually seen it. It is worth checking around to see what existing music resources are available. If there isn't a stake music library already, START ONE!!! It can start by just trading music with another ward choir director. The more wards you can get involved, the better. If 5 wards in a stake each buy 4 new pieces of music per year, that is 20 new pieces per year for your library. In 5 years, you will have a library of 100 pieces.
The Internet:
There are more and more resources now on the internet where you can
download music for free or purchase it and download it. There are also
databases of music that is now in the public domain (where the
copyright has expired) and may be downloaded/copied. Some websites where you can purchase music have an audio sample or a page of the score that you can preview.
Go Shopping:
If you are lucky enough to live near a music store with a good selection of LDS-appropriate choral music, go and browse. They may have a salesperson who can recommend some pieces that would be appropriate for your choir.
The LDS Hymnal:
This suggestion will probably elicit groans from more than a few people, but I believe that the hymnal is an under-used resource. I am not one of those people who believe that ward choirs should ONLY sing the hymns- I think they should sing a variety of appropriate music. But-- choirs should sing the hymns too. Sometimes it seems like choir directors almost try to avoid the hymns, because they seem so ordinary. Your job is to make it so the performance ISN'T just ordinary. Really the problem is that many hymns are too hard for the average ward choir. To sing a hymn beautifully- with good dynamics, phrase shaping, breathing and intonation is not an easy task- it is quite difficult. But it is worth the challenge.
There are some classic, beautiful, familiar hymns that can never be sung too much, as well as beautiful, less familiar hymns that deserve more exposure. (Did you know that there are hymns in our hymnal composed by Mendelssohn, Haydn and Handel? Do some more exploring....) There are also good suggestions in the back of the Hymnal for altering hymns for singing by choirs. Consider asking members of the choir what their favorite hymns are and singing one of those.
Other Hymnals:
There are other hymns out there that did not end up in our current hymnbook that are still worthy of being sung ("Come Thou Fount Of Every Blessing," anyone?). You can also check older versions of the hymnal for different hymns or for a different keys/arrangements of current hymns. Check around and do some exploring and you may find some gems. However, if using a non-LDS hymn, make sure the text is doctrinally correct and the musical style is appropriate.
Mormon Tabernacle Choir
I often get ideas for new music from listening to the Mormon Tabernacle Choir, either their CD's or in General Conference. The conference issue of the Ensign has a list in the front of all of the choral arrangements that were sung in General Conference. I have also found new repertoire from the CD's released by the BYU choirs. Some of what they sing is too difficult for the average ward choir, but if you look, you can find some of their repertoire that is within the range of a ward choir.
Local Talent:
You may happen to have someone in your ward/stake who can compose or arrange music. Maybe you have a good pianist or organist who can make up and accompaniment to a hymn or add interludes in between verses. Or maybe you have a violinist or other instrumentalist who can write an obbligato to play with the choir.
DO NOT PHOTOCOPY MUSIC ILLEGALLY!!!!
I know that there are some people buy a single copy of music and photocopy it for the choir to use (and in many places this unfortunately is standard practice), but THIS IS ILLEGAL. When you do this IT IS NO DIFFERENT THAN IF YOU WALKED INTO A MUSIC STORE AND STOLE THE COPIES. This seems to be difficult for some people to understand because there just isn't the same twinge of conscience at walking up to a copy machine as there is to sneaking out of a store with music under your jacket, but they are THE SAME. Stealing music hurts the composers/arrangers who have used their time and talents to publish the music, it hurts the publishing companies and it hurts the music stores. Even if you don't care about any of that it is still wrong.
Luckily, even if you have a music budget of zero to nil, there are lots of resources out there. There are many sites on the internet that have music available to download for free. How can you tell if it is legal to copy: it's quite simple. Look at the beginning of the piece and it will either say, "This may be copied for such and such a use" or "This may not be copied." When in doubt, don't.