CatholicCulture.org (formerly PetersNet.net) [ very highly recommended ]
IntraText Digital Library of Religion
Archivum Liturgicum Sacrosantæ Romanæ Ecclesiæ
catholic.ru features a superb library of Papal and ecumenical documents in Russian and a lithurgical calendar with colors and Scripture readings for every day.
An unofficial Website of the Catholic Church in Russia.
Католическая энциклопедия [Catholic Encyclopedia in Russian]
David Forster's Liturgia Latina (Aberdeen, England)
Michael G. Powell's An Introduction to the History of Christian Liturgy in the West (Yale University)
Walter J. Ong, S.J., a theorist of communication and literacy
The Papal Visit to Ukraine site which contains important information and photos about this historic visit, as well as information and portraits of the beatified first two exarchs of the Russian Byzantine Catholic Church, Blessed Leontios Feodorov and Blessed Kliment Sheptytsky.