CanticaNOVA
Describes itself as a source of "traditional music for the contemporary (Catholic) Church". Also has a liturgy planner.

Cyber Hymnal
This site has over 2,900 Christian hymns and Gospel songs from many denominations. The site contains an extensive collection of lyrics, scores, MIDI files, pictures, history, and more available for viewing and downloading.

Iona Community
Music by John Bell & the community; publication now covered by GIA but lots of great ideas/resources for liturgy & ecumenical Christian life in general.

John Michael Talbot
The well-known composer John Michael Talbot is covered by OCP, but also has an interesting website of his own.

Holy Rosary Cathedral (Regina) Music Home Page
Suggestions for Sundays, funerals and weddings.

National Association of Pastoral Musicians (NPM)
Great website including music-planning-calendar quoting sources in most major hymnals & lots of others you'll never have heard of...

Royal School of Church Music
Choral/organ/chant. More Anglican-based, but music is universal... RSCM is based in the UK, but catering for the international church.

Sacred Music Society (SMS)
The Sacred Music Society (SMS) An organisation which seeks to preserve and nurture high quality church music, and to encourage its use in liturgical settings. The SMS concentrates primarily on sacred music of the classical genre from Gregorian chant to the late romantic era. Web site contains information on the activities and concerts organized by the SMS, as well as a music section.

Saint John's Abbey
Includes links to Worship, University and Liturgical Press.

Taizé
Wonderful site about the Taizé community, their music by Jacques Berthier (now published by GIA), their prayer, liturgies, writings of Brother Roger, and more...

The Ames Hymn Collection
A collection of over 250 traditional church hymns, complete with lyrics and audio.

The Order of Saint Benedict
Links on liturgy and music.

The Vatican
The Holy See Vatican web site.