AMP: Artists' Meeting Place and Resource Collective

Art World Dealers: The Leading Art and Antique Dealers of the World
* From their catalog, which can also be accessed online: "Our aim is to inform those who are interested and involved in the world of art and antiques about the activities and specialities of more than 350 dealers from 15 countries." Countries include Argentina, Belgium, Canada, China, France, Germany, Italy, Monaco, Netherlands, Portugal, Spain, Sweden, Switzerland, UK, USA.
http://www.artworlddealers.com

ArtLondon.com
An online fine art marketplace, featuring paintings, prints, and photographs in a range of genres and styles by international and UK based artists. Also features arts stories.
http://www.artlondon.com