Yesterday, I created a bookmarklet which is now featured (as of of many implementations) on Jon Udell’s LibraryLookup (Innovative Interfaces libraries). Thanks Jon.
The bookmarklet is rather special. If you are on any webpage about a book, and the URL has the ISBN number somewhere in it, clicking on the bookmarklet will bring up a window with a message about whether the book is available in a public library.
In Udell’s and others implementations, the bookmarklet interacts with one library’s database. In the Danish case, it is a bit more advanced. Because we have bibliotek.dk which is not a library, but a database of holdings in all danish libraries, the bookmarklet searches all public libraries at once. Via bibliotek.dk, you can send an order to your local library (regardless of which library owns the material) and after a few days pick up the material from your own library.
I have no affiliation to bibliotek.dk, and just went to their site and played around with the URLs (badly designed? or is there an idea?). Danish Bibliographic Centre runs the site. library.dk is an English language interface to the database.
I searched for some info about the technology behind bibliotek.dk. It seems they use some old Z39.50 technology, but are adding XML.