The John Johnson Collection is active on Twitter: @jjcollephemera. Why not follow us?
And, when we have time, we post to: The John Johnson Collection: Now and Then, an occasional blog about the Collection.
With the caveat that The John Johnson Collection Ephemera Resources blog is no longer updated, it nevertheless constitutes a useful starting point to explore other collections of printed ephemera, with each entry having multiple tags, such as #artists, #prints, #exhibitions, #postcards, #image galleries, #posters, #political cartoons. There are guest posts too.