Naomi Symes
Books on social history and women's history; out-of-print, antiquarian and in-print titles.
http://www.naomisymes.com/

Netsifters
Antique, old, first edition, author inscribed, rare, limited edition, scarce, small press, out of print, remainders, and used books organized into many categories.
http://home.earthlink.net/~netsifters/

Newport Book Store
Fine, new and rare books, specializing in Americana, military history, intelligence and espionage, with an emphasis on the American Revolution.
http://www.nptbooks.com/

No Garbage Books
Includes a search feature, links to other book sites, and local history.
http://www.nogarbagebooks.com/

Nudelman Rare Books
English and American Literature, Art Nouveau, Children's books, Victorian and Pre-Raphaelite rare books. Requires acrobat reader.
http://www.nudelmanbooks.com/