Here is an item that may be of considerable interest to priests, scholars, liturgists, translators, composers, et alia -- the entire LATIN TEXT of the Ordinary Form of the Missale Romanum, with all the fixed and changeable parts of the Mass and the complete lectionary of readings, psalms, and Alleluia verses.
Corpus Christi Watershed has made available a high-quality scan of the four volumes depicted at the left, adding up to a total of 7,777 pages -- no, I'm not making that up!
Although they carry a publication date of 1977, not so much has changed in subsequent MR editions that this first edition would cease to be useful. And of course, for study of the original edition, it is an indispensable resource.
From what I can tell, these books are extremely rare, so it's nice to see them finally made available electronically to the public.