Analecta hymnica medii aeviGerman hymnal by Guido Dreves, published in 1886 and available online through Open Library
CanticaNOVAIf you're involved in liturgical music, this site could be a valuable resource.
Hymn Tune IndexThe HTI database contains all hymn tunes printed anywhere in the world with English-language texts up to 1820, and their publication history up to that date.
Liber Usualis onlinePublished by the Church Music Association of America, this is a file that can be downloaded to your hard drive.
Musica SacraHome page for the Church Music Association of America where you can download music, sheets, and find other information about sacred music.
NetHymnalA search engine with over 10,000 Christian hymns,Author Bios, Composer Biographies, Hymn Histories and Gospel songs from many denominations.
