Aziomedia
Includes titles from all genres, first editions, and ephemera. All books are cleaned and covered.
http://www.aziomedia.com

Bondi Books
Offers a visual book catalog. Located in Japan and ships worldwide. Order by email.
http://www.bondibooks.com

Book Lady Used Books
Specializes in gently used paperback, hardcover, and audio books. Order by email.
http://bookladybooks.com

Book-Bin
Specializes in used books and videos. Has rare books as well as current releases.
http://www.book-bin.com

Book-Smiths
Offers paperbacks of popular fiction, mysteries, and romance. Also has selection of food, cookbook, recipes, biographies, autobiographies, self-help and advice.
http://www.book-smiths.com/

Books Maps Prints More
Offers used, out of print, and fine books on a variety of subjects. Sells decorative collectible and antiquarian prints, maps, ephemera, magazines, and catalogs.
http://www.booksmaps.com

Cheap Thrills
Used, rare and collectible books. Focuses on reading copies of mystery, intrigue, and romance. Order by email.
http://www.webrighter.co.uk/cheapthrills/

Christine Kovach, Bookseller
Catalog of modern first edition science fiction, fantasy, horror, and mystery titles. Many signed books.
http://www.kovachbooks.com/

Cobblestone Books
Specialties include science fiction, fantasy, horror, mystery, and pulps. Catalog is updated weekly.
http://www.cobblestonebooks.com/

El Pinarillo Books
Internet-only bookstore which buys, sells, and searches for quality secondhand books. Located in Spain.
http://www.elpinarillobooks.com

Fiction Addiction
Sells used fiction of all flavors, including science fiction and fantasy, horror, mysteries and thrillers, children's and young adult, romance, contemporary fiction, paperbacks, hardcovers, audiobooks, and collectibles.
http://www.fiction-addiction.com/

Gnu Books
Includes general fiction, romance, science fiction, horror, mystery, spy and adventure, and children categories. Both paperback and hard cover books.
http://www.gnubooks.net

Grace's Romantic Reading
Used novels, including fantasy, historical, horror, mysteries, and romance paperbacks.
http://www.romanticreading.com/

Laurie J Books
Features gently used paperback and audio books. Most books have scanned cover images.
http://www.lauriejbooks.com

Nora's Book Nook
Offers fantasy, mystery and romance used books. Order by email.
http://www.norasnook.com/

Now and Then Books
Sells used fiction of all genres, including science fiction, fantasy, horror, mysteries, thrillers, children's, young adult, romance, and contemporary fiction.
http://nowandthenbooks.com

O'Briens Book Cellar
Rare, hard to find, children's, hardcover, and collectible books. Large collection of copyright-free, public domain ebooks.
http://www.obrienbooks.com/index.html

Pazzo Books
Carries selection of used books with particular strengths in 20th century fiction, children's, and the social sciences.
http://www.pazzobooks.com

Pywrit Used Books
Specializes in science fiction, fantasy, horror, and romance fiction paperbacks.
http://www.pywrit.com/

The Book Cave
Dedicated to the sale of secondhand books, annuals, comics and magazines. Find Enid Blyton, bestsellers, Commando comics, The Muppets, and Dr Who. Order by email.
http://www.thebookcave.com/

Vintage Library
Books and information on authors from the early 20th century and the pulp fiction era.
http://www.vintagelibrary.com/

Violet Books
Specializes in hard to find antiquarian supernatural literature. Site covers a fairly broad range of late 19th and early 20th century fantasy literature.
http://www.violetbooks.com/