Medieval and Early Manuscripts
Digital Medieval Manuscripts at Houghton Library
http://hcl.harvard.edu/libraries/houghton/collections/early_manuscripts/
Digital Scriptorum (Columbia University Libraries)
http://www.scriptorium.columbia.edu/
Catalogue of Digitized Medieval Manuscripts. (UCLA)
http://manuscripts.cmrs.ucla.edu/
Early Manuscripts at Oxford University.
http://image.ox.ac.uk/
Parker Library (Corpus Christi College, Cambridge).
http://parkerweb.stanford.edu/parker/
538 Medieval Manuscripts, including one of the largest collections of Old English.
Early Printed Books
Bavarian State Library, Munich
15th century Bavarian Blockbooks
Bookbindings
Hand Bookbindings: Plain and Simple to Grand and Glorious (Princeton Special Collections)
http://libweb5.princeton.edu/visual_materials/hb/index.html
General Collections of Primary Resources
World Digital Library
http://www.wdl.org/en/