"lib-web-cats (library web sites and catalogs) is a directory of libraries worldwide. While the majority of the current listings are in North America, the numbers of libraries represented in other parts of the globe is growing. Each listing includes links to the library's website and online catalog. Other information available includes the geographic location, address, library type, current and previous library automation systems used, and the size of the library's collection."

Useful for seeing which libraries use which ILS/OPAC 

A blogpost from LibraryCrunch listing great additions to the library catalog of the future.