The two groups most commonly associated by search engines as being interested in things like link data and information retrieval technology, outside of their own engineers, are librarians & SEOs. The first group are typically lauded while the second receives both internal and external flak on a regular basis (not that I'm complaining - they're well within their rights).

However, as a whole, librarians and the massive projects they undertake to organize and disseminate the world's information have been largely ignored by the SEO community, perhaps due to a seeming lack of direct relevance. However, there is a lot to be garnered from librarian authored resources on the subject of organizing the Internet and on search engines themselves. I've listed just a few valuable resources below:

1. The Librarian's Index to the Internet
   While this resource is by no means as comprehensive as Yahoo! or DMOZ, it does offer a glimpse into how organizations might be structured by those outside the Internet field. Of considerable interest to me was the selection criteria, which offer some excellent suggestions for any directory or site seeking to be listed and ranked.
   
2. COPAC
   One of the largest resources available for purely academic research and books, this is a part of the hidden web, as virtually none of its holdings have been indexed by the SEs.
   
3. InfoMine
   A search engine and web directory creted by academic librarians. It's currently got about 3X as much as the LII and a good search engine to boot.
   
4. The Search Page
   An older, but nonetheless fascinating resource listing sites where specific types of vertical searches can begin - goes far beyond simple web search and into people finding, code research, mailing lists and much more.

There's a great deal of value to SEO/Ms on the web that has yet to be discovered and I hope to keep finding great resources like these. List any similiar contributions you might have found in the comments; I'd be thrilled to see more.