The Alexander Turnbull Library in Wellington, New Zealand, has launched a Tumblr page for its Rare Books & Fine Printing Collection:
http://turnbullrarebooks.tumblr.com
The page is off to a fun start, with topics ranging from medieval manuscripts and an eighteenth-century geometric binding, to decorative endpapers and the title-page of one of the Turnbull's copies of Aurora Australis, the first book published in Antarctica created by Ernest Shackleton.
A personal favourite is a closeup image of the pigments used on the illuminated title-page of a Persian manuscript:
If you like what you see and have a Tumblr account, do consider following and help build the library's follower base. Enjoy!