Google Art Palette - Unique color combinations, drawn from the world of art
WikiArt - The Encyclopedia of Fine Art
Magnus - Shazam for art
ArtMajeur - +1 Million original artworks, Free Shipping Worldwide, Low prices guaranteed, 14 days return: buy all the art you love on Artmajeur!
Artsy - A global platform for discovering and collecting art.
Saatchi Art - Online art platform for buying, selling and discovering art.