DIAMM - Portal to online images of Mediaeval music MSS (800 - 1500)
Facsimiles of Intabulatura de Lauto (1 and 2) by Francesco Spinacino
LSA Digital Facsimiles — Links to online facsimiles
MusRef - online music resources
National Union Catalog of Manuscript Collections - Library of Congress
Omifacsimilies - Facsimiles of music manuscripts and early printed editions