The Rylands collection at the University of Manchester
This collection displays highlights spanning five millennia from the vast resources of the Special Collections Division of the John Rylands University Library. It now contains over 6000 images and they are adding new images regularly. http://www.library.manchester.ac.uk/searchresources/imagecollections/university/rylands/
Perseus Project
Perseus is a growing collection of online resources for studying the ancient world. Materials include ancient texts and translations, maps, articles, essays, and images from over 70 museums around the world. http://www.perseus.tufts.edu/
The Labyrinth: resources for medieval studies from Georgetown University http://labyrinth.georgetown.edu/
Otto F. Ege Collection: Fifty Original Leaves From Medieval Manuscripts, Western Europe:
The items in this collection illustrate the art of the manuscript during the period of its greatest development and influence. From varied periods, national origins, and functionality, the documents in this collection provide a wide-ranging introduction to the art of the medieval manuscript.http://www.sc.edu/library/digital/collections/ege.html
The Foundation for Medieval Genealogy (FMG) is an official not-for-profit charity registered in England and Wales to promote rigorous scholarship in the field of medieval genealogical, prosopographical, and related research; to collect, catalogue, translate and analyse relevant primary and secondary sources; to undertake research projects, or to support such projects by financial or other means; and to disseminate information by electronic or conventional means.http://fmg.ac/
Dscriptorium, from Brigham Young University, is devoted to collecting, storing and distributing digital images of Medieval manuscripts http://toisondor.byu.edu/dscriptorium/