A number of volumes focus on French medieval literature:
Some of these Companions are also available in print.Dictionary of Literary Bibliography: An extensive scholarly reference book covering authors, books and various topics in literature. Each chapter provides a bibliography.
Refworks allows you to create a personal database of references and automatically generate formatted bibliographies for your projects.
The digital library of the French Bibliothèque Nationale provides online access to the full text of numerous French works, including several editions of La vie de Saint Alexis, La Chanson de Roland and to Le miracle de Théophile. It also has critical studies on these as well as on Le roman d'Eneas, Tristan et Yseut, Merlin and Le chemin de longue étude.
An online database of French language scholarly journals in the humanities, it includes numerous materials on French medieval literature.
A wonderful online exhibit of the Bibliothèque Nationale de France, it contains in-depth information and beautiful illustrations, including pages on Merlin and Chrétien de Troyes, and digital versions of Histoire de Merlin and other volumes.
Another exhibit of the BNF, it contains images, videos, digital versions of Roman de Renart and other works, and much more!