The Art History Research Center  
Includes article indexes, university departments, online art collections, and other art history web resources.

Art History Resources on the Web 
A near-exhaustive set of links to recent research and articles as well as photographic images of art pieces.  Also provides connections to other resources, such as museums, image banks and artist directories.

Axis
Aims to promote contemporary professional British visual artists to the public by demonstrating their contribution to social and environmental development. 

GraphicBrain.com
"GraphicBrain.com is a specialized search engine, focused on the technology and products used in the graphic arts, printing and publishing industry" Most searching available for free, but some requires a paid membership (yearly fee.)

Graphics.com
Offers product reviews and other interesting information pertaining to various types of digital design.

National Portrait Gallery
A slick, well-organized accompaniment to the United Kingdom's National Portrait Gallery.  Features include visitor information, research facilities, advanced searches, a picture library & press releases.