BVMM: Bibliothèque virtuelle des manuscrits médiévaux , a virtual library of medieval manuscripts in French Libraries by the Institut de recherché et d’histoire des texts in Paris (IRHT-CNRS).
CERL Portal (Consortium of European Research Libraries): This database cross searches a number of European and Yale's manuscript collection catalogues as well as the Hand Press Book database, which lists books printed between 1450 and 1830.
Inside a Book of Hours. Although their contents varied widely depending on the date and place of production, most Books of Hours possessed certain common elements. The most important and frequent of these elements are described here (Harry Ransom Center).
Medieval Manuscript Manual. This site offers basic information about Medieval Manuscripts, including their production, structure and function. There is also a glossary. The site was created by the Department of Medieval Studies at Central European University, Budapest.
Palaeography: Reading Old Handwriting 1500 - 1800. An on-line reference and tutorial in palaeography created by the National Archives of the United Kingdom.
Understanding Illuminated Manuscripts: A Guide to Technical Terms Illustrated glossary by Michelle Brown