auctionata

[Update March 2017 - auctionata has suspended its activities] Auctionata is a German start-up which was founded by 2012 by Alexander Zacke, a former, talented eBay power-seller. The huge success today of the company makes it a major online competitor for the biggest auction houses.

artnet

Artnet is the leading resource for the international, online art market, allowing to access results of auctions and buy from partner galleries or via online bidding.