Library Catalogs on the Web

Library of Congress Online Catalog
The de facto national library of the United States and the research arm of the United States Congress.
The European Library
Portal which offers offers the ability to search the Union Catalog of Europe’s National Libraries.
The Karlsruhe Virtual Catalog KVK
A meta search interface which allows access to library and book trade catalogs via WWW.
Western European Library Catalogs
Union catalogs and groupings arranged by country.
WorldCat Advanced Search
Search interface of a cooperative database of bibliographic records.