Library Indexes (http://www.libdex.com)
Libdex is a worldwide directory of library homepages, web-based OPACs, Friends of the Library pages, and library e-commerce affiliate links. 

Library of Congress Catalog(http://catalog.loc.gov/)
The entire Library of Congress, at your fingertips. 

New York Public iPac Library Catalog(http://catnyp.nypl.org)
Web version of the catalog of the New York Public Library. 

Newburgh Free Library HomePage (http://www.newburghlibrary.org)
Local, with great links. 

Ramapo Catskill Library System (http://www.rcls.org)
See everything your library system does for you! 

Vanderbilt University Catalog (http://acorn.library.vanderbilt.edu/uhtbin/webcat)
The catalog of Vanderbilt University.