Artists, arthistorians and collections
RKDartists&
The Getty Union List of Artist Names (ULAN)
Repertory of Dutch Mapmakers 1500-1900
Sikart (artists from Switserland and Lichtenstein)
Dictionary of Australian Artists Online
Monogrammists (in Italian)
Also see:
Biografisch Woordenboek van Nederland (in Dutch)
Dictionary of Art Historians
Dutch architects
Collections in the United States
The Frick Collection: Archives Directory for the History of Collecting in America