Liturgica.com is a website I have found quite interesting for a time. It is particularly good though for its sacred music, which it divides into Western, Eastern and even Jewish. Moreover, it links you to CD's of numerous quality recordings of liturgical music from these traditions and, even better, gives you a liberal dosing of it right on the website itself, along with numerous other clips.
liturgical music and liturgical books -- Liturgica.com
I found it intriguing how similar Jewish liturgical chant is to Christian chant. It was an eye opener for me when I first discovered this, and I remember a religious brother whom I was with at the time who said "there's our ressourcement." In that vein, when we throw away our chant, we are throwing away a great deal of the patrimony, not only of the Christian Church, but also of the Jewish tradition of which Christianity is the fulfillment.
Incidentally, there's lots more than just music on the site, so take a look.