Stackstreet Books
- Rare literature, first editions, poetry, science-fiction, graphics, New Zealand.
- http://www.abebooks.com/home/STACKST9/

Sunbow Books
- Used books searchable by author, title or keyword.
- http://www.tomfolio.com/mall/sunbowbooks/

Significant Books
- General books, also with a specialist interest in science and technology.
- http://www.significantbooks.com/

Studio Bibliografico san Mamolo
- Specializes in old and used books about nature, science and history. Also in Italian.
- http://www.diecidieci.com/mamolo_new/

Schwartz Judaica
- Out-of-print books of Jewish interest from art to Zionism, in various languages, including English, Hebrew, Yiddish, and German.
- http://www.schwartzjudaica.com/

Seasoned Books
- Specializing in books on sustainable lifestyles, wilderness adventures and renewable energies.
- http://www.seasonedbooks.com/

Signed Books
- A collection of new books that have been signed by the authors.
- http://www.signed-books.co.uk/

Symposion Books
- Auction hall and online antiquariat.
- http://www.symposionbooks.com/

Sage Old Books
- Modern first editions, author signed books, Australiana, plus wide range of 19th and 20th century used books.
- http://www.sageold.com.au/index.shtml

Stone House Books
- Specializes in modern first editions, collectible children, science fiction, horror, mystery and Edgar Rice Burroughs "Tarzan" books.
- http://www.stonehousebooks.com/

Savoy Books
- Specializing in horticulture and agriculture, historical Americana, English and American literature.
- http://www.vgernet.net/frakerbook/

Sangraal Books
- Used books, in browsable categories, including fiction, philosophy and fantasy.
- http://sangraal-books.com/

Serendipity Books Michigan
- Used, rare and out of print books. Specializing in nonfiction including science, history, religion, and social sciences; based in Michigan.
- http://www.serendipitybooksinmichigan.com/

Simpson Books
- Specializing in modern, out-of print, first edition collectable books, many signed by the author.
- http://simpsonbooks.com/

Second Story Books
- Used books; Mystery and Science Fiction catalogues issued regularly.
- http://www.secondstorybooks.com/

Steve the Fish
- One man business selling first editions and collectable books.
- http://www.stevethefish.co.uk/

Serendipity Books Berkeley
- Used and rare books; based in Berkeley, California.
- http://www.serendipitybooks.com/

Sumner and Stillman
- Antiquarian Booksellers, specializing in nineteenth century British, Irish and American literary first editions.
- http://www.sumnerandstillman.com/

Skriptoriet Used Books
- Scandinavian used and antiquarian books and online entry of book location requests. Bilingual, Swedish and English.
- http://www.skriptoriet.se/

Sigler Press
- Out-of-print books about Biblical studies, theology, church history, and pastoral care.
- http://www.siglerpress.com/

Sleepygirl's Used Books
- An internet only used bookstore.
- http://www.sleepygirlsusedbooks.com/

Sheila Markham Rare Books
- The East; exotic printing, calligraphy and general antiquarian books.
- http://www.sheila-markham.com/sheila_markham.html

Signed Rare Books
- Signed rare books, modern first editions and antique books.
- http://www.signedrarebooks.com/

Second Life Books
- Antiquarian and out of print books by and about women, first editions of literature, agriculture, and horticulture; a range of printed and manuscript material from the 16th to the 20th century.
- http://www.secondlifebooks.com/

Sean Fagan, Rare Books
- Book seller offering a searchable database and photographed catalogs of scarce books in many fields.
- http://www.faganbooks.com/

Scrinium Classical Antiquity
- Secondhand and antiquarian books on classical antiquity. Online catalogues available.
- http://www.scrinium.nl/