Lobby Card Invasion http://www.lobbycardinvasion.com
Selling original, authentic Hollywood movie posters and lobby cards. Large searchable database, auctions, trading, and special deals for online customers.
Arnold Movie Poster Company http://www.movieposters.com/
Buys and sells old movie posters, lobby cards, and stills (photos). Features a wide variety of original posters covering the obscure to the well-known, but deals mostly with older posters.
Posterplanet http://www.posterplanet.net
Features movie posters, celebrity posters, TV posters, and music posters. Originals and reproductions. [Java plugin required]
Vintage Poster Art http://www.vintageposterart.com
Vintage US and European movie posters, as well as advertising posters dating from the 1890's. Information on collecting and preserving vintage posters.