Jackman Music Express www.jackmanmusicexpress.com
LDSMusicSource.com http://www.ldsmusicsource.com/index.html
This website has a large catalog of pieces, mostly SATB LDS Hymn arrangements. You download the music and print/copy it, then you order green labels that they send you in the mail that make each copy legal. One great feature of this site is that you can listen to the piece (via midi file) and review the score before you purchase it. This can be very helpful, especially for choir directors who don't play the piano.
Choir Works: Music of M. Ryan Taylor http://www.choirworks.com
Teton Music (Michelle Willis) http://www.tetonmusic.com/ldscatalog.htm