ViaLibri
Search multiple sites to verify and locate old, rare, and out-of-print books.
Out of Print Books
AbeBooks
A network of used bookstores, listing over 28 million titles for sale.
Biblio.com
Used, textbooks, rare, and out-of-print books from a global network of independent booksellers.
BookFinder
A comprehensive book search engine that includes 30,000 new and used book dealers and databases to find over 50 million new, used, rare, and out of print books
Alibris
Another network of used bookstores and rare book dealers, which includes free shipping on larger orders and special services for librarians and collectors.