Anthony Robinson, of Penn State, is going to offer a free MOOC on Maps and the Geospatial Revolution, starting in July 2013. Dr. Robinson has also provided a YouTube video to explain the themes of the course.
h/t Donna Genzma
A portion of the holdings in these collections have been optimized to allow searching for elements within a given map, such as sea monsters, decorative borders, cartouche, or other imagery. This search screen will allow you to search these elements, but remember it is only searching a fraction of the collections.