Booked for Murder
Independent bookstore specializing in new, used, rare, and collectible mystery books.
http://www.bookedformurder.com/

Detective Fiction
Exclusively offers crime and mystery fiction with free delivery worldwide.
http://www.detective-fiction.com

Fyrbyrd Bookshop
Carries mystery and suspense, from whodunits, police procedurals, famous detectives, noir, and true crime. Also sells rare medical books.
http://www.fyrbyrdbookshop.com/

Grave Matters
Offers new, used, and out of print mystery, detective fiction, and related reference material.
http://www.gravematters.com

Regarding Books
Collectible bookseller specializing in mystery and modern first editions.
http://www.regardingbooks.com/

The Mystery Bookstore
Signed first editions, rare and collectible, new and used, children's. Shop instore (Los Angeles) or online.
http://www.mystery-bookstore.com/blog/