be Books has a treasure trove for those of us who like to gaze upon old books, far beyond our means, and dream. I speak of the Abe Books Rare Book Room. And in that virtual room, is the Illuminated Manuscripts section, which holds things like: an illuminated Morte D'Arthur: A Poem, by Lord Alfred Tennyson (sold), a single page from a 1460 copy of a Book of Hours, and books about illuminated manuscripts and their history.
In the introduction to the Abe Books Illuminated Manuscripts section, Beth Carswell tells us that the word 'manuscript comes from the Latin manu scriptum, which translates literally to "written with hands".' Go Monks!
New York Public library has a vast illuminated manuscript collection, many images of which are available on-line. They don't say much about the collection, and the entrance page on the site has 3 or 4 links that seem like they'd be helpful, but not one of them works. The connections to the images via the contents page however, works fine. And the images are beautiful! Just check out this image of the Annunciation and beginning Hours of the Virgin in a copy of the Book of Hours.
The Library at the University of Glasgow has--or had--a Book of the Month page in their Special Collections department. They're on holiday from this while they re-design their website (so the link may not work indefinitely). The last entry before the hiatus, December 2009, brought what they call their "jewel in the crown of illuminated manuscripts: Ludolph of Saxony’s Vita Christi (or Life of Christ)", which they describe this way: "A devotional account of Christ's life, this substantial French manuscript is comprised of four volumes containing 140 illuminated illustrations." Its pretty sweet.