My library does not currently use Pinterest. I know lots of libraries do, especially larger and public libraries (like NYPL), and it's been a really great way to interact with patrons and get information out about programs and resources. Check out this article to see a bunch of neat applications.
NYPL's Pinterest boards include photos from their archives, infographics about the library, current reading lists, and, of course, pictures of cats.
It seems obvious that such a large and well-endowed library would have plenty to post about. They have such an interesting and extensive collection that having a glimpse into it, even virtually over social media, is exciting. Just check out their "Collections" board.
But I'm skeptical as to what value Pinterest would have for a small academic library such as my own.
The best ideas I can come up with are more for novelty's sake than anything--linking our catalog holdings with displays, or holidays, or current events. And even then it would require hunting for photos of book covers. Plus something like that might be interesting to look at, but has no viral value--not many people would be "repinning" such things. Unless perhaps they had a "To Read" type of board.
Or maybe it could be an interesting way to display books on Reserve--have a board for each course with pins for each text?
In any case, it seems like more work for little return on investment.
Have you seen valuable ways for libraries to use Pinterest? Does your library pin?