A tip of the hat to Linda White for pointing this out!
This website is a "finder" tool, to help you find exhibits on the web. It's hosted by the Smithsonian Institution Libraries.
Here's a description taken from the site:
This site features links to online exhibitions that have
been created by libraries, archives, and historical
societies, as well as to museum online exhibitions with
a significant focus on library and archival materials.
These online exhibitions draw their inspiration and
content primarily from library and archival materials,
including, for example: printed books, book illustrations,
manuscripts, photographs, printed ephemera, posters,
archival audio and video recordings, artist's books, and
the book arts (engraving, marbling, and bookbinding, etc.).
The online exhibitions in this guide are listed alphabetically
by title. A keyword search engine for this site is currently
under development, to facilitate access to individual
exhibitions by subject, geographic location, and institution.