Latin and Orthodox Resources for choirs and scholars

Listen to plainchant has the best bibliography if you are interested in learning about Gregorian chant.

Abbey of Solesmes
Byzantine Chant Sheet Music Page
CANTUS-database for Latin Ecclesiastical Chant
Catholic Church - Liturgical Tables
The Gregorian Association (London, England)
Listen to Plainchant (probably the most comprehensive and useful site)
Latin Dictionary
Lexicon musicum Latinum
Musica Sacra - Church Music Association of America (includes important chant resources)
Prayers - LATIN TRANSLATION
Church Latin (pronunciation guide)
Roman Chant and Liturgy
Thesaurus Musicarum Latinarum
The Vulgate Online

The work in English on Latin pronunciation is Harold Copeman's Singing in Latin (ISBN 0 9515798 2 7), revised edition, 1992.
This work was self-published in Oxford and is an exhaustive analysis of pronunciation by period and region.
There is also 'The pocket 'Singing in Latin'' and small ring bound summary designed for choristers
(ISBN 0 9515798 1 9)- quite handy.

A later work that has input by Copeman is McGee, Rigg and Klausner's Singing Early Music, Indiana University Press, 1996. This has extended sections on the pronunciation of Latin by region and period and has an accompanying CD of recorded examples of pronunciation also but is not as comprehensive.
This book is not limited to Latin