Many libraries around the world house fantastic digital collections available at your fingertips for free! For some, it is daunting to poke around trying to find something specific when there is such a wealth of information on hand. The Bodleian Libraries at Oxford shared this helpful quick video of how to navigate their online collection: Navigating the digital collections
Though the Bodleian Libraries has an extensive collection to browse, I personally enjoy the manuscripts available from the Polonsky Foundation Digitalisation Project.
I've spent time browsing fantastic 12th century pieces like this Greek Psalter (dates c. 1105 to be more precise):
I highly recommend having a look at their collections for both academic and personal interest. Shortly I will also be featuring more specific pieces along with interviews from the National Library of Scotland that holds many treasures of its own!