Clickable: Down With The Dewey Decimal System
The link for this is one of the coolest real-world systems I have ever worked with. It is an international library resource searching tool. You can literally search for books, videos, music, etc. (all that a library would offer) at your surrounding libraries; without even having to know if a library exists or where the library is in your area.
For example, I wanted to find a book on php programming; so I just typed in the keyword ‘php’ and it found me a list of potential books (and other resources). Then I clicked on the book I was interested and it listed to me all of the local library systems that I could get the book from.
The way it works is that it brings together all of the local library catalog systems together into one master system. So whenever I am out of town and I need to find a particular resource I can just search and find out what local branch I could swing by to take a look.
One of the other cool things I learned about libraries is that some of them offer live chatting services with their branch librarians (and this site hooks directly into those as well).