- Archivum Liturgicum Sacrosanctæ Romanæ Ecclesiæ
- A complete collection af all Liturgical Books of the Roman Catholic Church, following the traditional latin rite.
- Bernard Gui on the Albigensians
- A first hand description of the Albigensians’ beliefs and practices from the Inquisitor’s Manual of Bernard Gui [d.1331], early 14th century. Site maintained by Fordham University.
- Bibles
- The Bible in French, English, Latin, and German translations. Part of the ARTFL project at the University of Chicago.
- Cistercian Order
- Includes a history of the order, descriptions of historic Cistercian abbeys and the Charta Caritatis in English.
- Cistercians in Yorkshire
- Site contains the histories, personalities and 3D floor plans of 5 Yorkshire Cistercian abbeys: Fountains, Roche, Kirkstall, Byland, and Rievaulx. Additional focus is given to an overview of the orders’ practices as well as the lives of monks, lay brother
- Dore Abbey
- The Cistercian monastery of Dore Abbey, founded in 1147, was located in the Golden Valley on the Welsh border. It was dissolved in 1537 and reconsecrated in 1634 as an Anglican, Laudian, Church.
- Early Church Fathers
- A 38-volume collection of writings from the first 800 years of the Church. This collection is divided into three series, the Ante-Nicene, Nicene, and Post-Nicene Fathers.
- Eckhart Society
- This site promotes the study of the teachings of Meister Eckhart(c. 1260 – 1327/8), one of the great Christian mystics of the Dominican order. Biography, academic resources and web links available.
- Ecole Initiative
- A hypertext Encyclopedia of Early Church History on the Web. Excellent research resource, well organized.
- Fourth Lateran Council: Canon 3 on Heresy 1215
- Text from a disciplinary decree of an Ecumenical Council. Maintained by Fordham University.
- Guide to Early Church Documents
- Contains canonical information, documents by the Apostolic Fathers, many Patristic texts, creeds and later documents.
- Heresies
- A brief description of ‘heresy’ with links to information on several of the major heresies. Includes brief bibliography. (At Kenyon College)
- International Anchoritic Society
- Society of scholars whose research focuses on medieval anchoritic texts and traditions.
- L’Abbaye Saint Germain d’Auxerre
- Comprehensive overview of the Abbey with detailed 1500 year history, photos, and architectural plans.
- Lollard Society
- A site and a society devoted to the study of Lollardy and the religious culture of the later middle ages in England.
- Oliviana
- An electronic journal devoted to Peter John Olivi and the Franciscan Spirituals, XIIIth-XVth Cent., publishing critical editions of unpublished texts and original researches. Papers are in English, French and Italian.
- Order of Saint Benedict
- Includes a history of the order and the Benedictine Rule in Latin and translations in English, French, German, Hungarian, Italian and Spanish.
- Paternoster-Row
- Paternoster-Row is a website about the history of medieval rosary beads, paternosters, and prayer beads, with illustrations, replicas, and bibliography. Abundant references to existing paintings and surviving medieval beads.
- Projekt Pseudoisidor
- An ongoing new edition of Pseudo-Isidore’s False Decretals.
- St. Pachomius Library
- Includes writings of the Church Fathers, the acts of the Christian martyrs, the proceedings of the Councils, and the lives of the early saints. Part of ‘The Orthodox Christian Page.’
- Two Thousand Years of Catholic Writings
- This page lists Catholic writings that can be read online, listed by author in roughly chronological order.
- Voyage en Terre d’Oc, le catharisme
- An extensive interactive encyclopedia of French Catharism. (site in French)
- YperLiberExtra
- YperLiberExtra provides the on-line text of Gregory IX, Liber Extra (1234), edited by Aemilius Frideberg in 1879. With a simple and friendly interface, it is possible to access the Gregorian text and then examine the correspondence.