Ann's Used Book Nook
Many paperback romances, thrillers, mysteries, and fantasy books.
http://www.annsusedbooks.com/

Paperback Trade Inn
Carries full lines of all fiction genres with specialist section for romance books and collectibles.
http://www.paperbacktradeinn.com/

Rainy Day Paperback Exchange
Carries fiction and nonfiction selections along with children's books. Ships internationally.
http://www.rainydaypaperback.com/

Taovision Enterprises
Features collection of quality vintage items at bargain prices, including paperback books, pulp magazines, comics, and movie memorabilia.
http://home.znet.com/taovision/