The LangChain Hub (announced here; examples here) provides prompts directed at developers integrating LLMs into systems (so not necessarily prompts refined for searching in these public-facing interfaces).
re: a “searchable repository of examples” (Zamfirescu-Pereira et al., 2023)?
The LangChain Hub does provide a search interface to the prompt examples.
Added September 13, 2023 09:48 AM (PDT)
I do not believe the LangChain Hub was initially searchable. I did not document this as well as I should.
Reference: The screenshot on blog.langchain.dev/langchain-prompt-hub shows a search interface on the hub. It is a bit disorienting as the og:image shows the search interface, even on tweets with social share cards from much earlier (and with gifs). The screenshot on docs.smith.langchain.com/hub/quickstart 
does not show a search interface, while the Google WebCache from 2023-09-09 ) does show a search interface. (It is possible it was only available to select accounts?) The screenshot from Google Images does not show a search interface 
. The screenshots on a 2023-09-08 article from Cobus Greyling (“LangChain Hub” ) and a 2023-09-10 article from Sudarshan Koirala (“What Is LangChain Hub” do not show a search interface.
I noted access to it on 2023-09-12.
I learned here of Mollick’s use of “grimoires” (Mollick, 2023):
As LangChain and the broader ecosystem has evolved, the role of prompting has only become more important to the LLM development process. As Ethan Mollick recently wrote [ . . . ], “now is the time for grimoires.” By “grimoires” he means “prompt libraries that encode the expertise of their best practices into forms that anyone can use.”
[ . . . ]
Today, polished prompts and the wisdom that comes with it are distributed across the web and all-too-often buried in the crannies of blog posts, Twitter threads, and people’s head’s. By bringing all tis knowledge together in one easily-navigable place, we think we can accelerate the pace of development and learning together.
To use Mollick’s terminology–we’re starting with public grimoires today, but we’ll be enabling private, company-specific grimoires very soon.
References
Mollick, E. (2023). One useful thing. Now Is the Time for Grimoires. https://www.oneusefulthing.org/p/now-is-the-time-for-grimoires [mollick2023useful]
Zamfirescu-Pereira, J. D., Wong, R. Y., Hartmann, B., & Yang, Q. (2023). Why johnny can’t prompt: How non-ai experts try (and fail) to design llm prompts. Proceedings of the 2023 Chi Conference on Human Factors in Computing Systems. https://doi.org/10.1145/3544548.3581388 [zamfirescu-pereira2023johnny]