The Vatican Website
Congregation for Divine Worship and Discipline of Sacraments, with links to various official documents from the Congregation as well as papal encyclicals and letters relating to liturgy and the Eucharist.
United States Conference of Catholic Bishops
A variety of resources can be found on this site and through the USCCB bookstore.
University of Notre Dame Center for Liturgy
Various resources on the Eucharist and the revision of the Roman Missal.
Institute for Liturgical Ministry
Founded by Sister Jorce Ann Zimmerman. The site lists resources for parish liturgical ministers and others interested in liturgy.
St. Louis University Center for Liturgy
Has resources for every Sunday of the liturgical year.
For books and resources for liturgical ministers, scholarly books on liturgy and the Eucharist, and books on biblical, liturgical, and other aspects of spirituality.
Liturgy Training Publications
Resources for liturical ministers and scholarly books on various aspects of Eucharist and the Liturgy.
Reflections and a variety of resources on the Eucharist, real presence. Sponsored by St. Anthony Messenger.
A number of books and resources on liturgy and the Eucharist, for adults and children.