NEW LINK! The Tudor Book Shop
AbeBooks - search for out of print material
Alibris - Rare, Used and Hard-to-Find Books
Antiqbook - Antiquarian Booksellers on-line
Books Tell You Why - Rare, autographed, and out-of-print books, hand-crafted bindings in fine leather and first editions.
Hamilton Bookseller
ISBNdb - Free database of ISBNs and a price comparison tool
Oxbow Books and David Brown Book Company
Peter Taylor & Son - History and archaeology booksellers
Tom Folio
World of Books
Zubal Books - Focuses on academic and university press publications