Art Technique & Tutorials
Very nice site. Tutorials and galleries for painting, drawing, photo/digital, sculpture, printmaking, pastels, and ceramics.
A huge directory of everything arts & crafts.  Links to supplies and tutorials.

Gurney Journey
Amazing blog from master artist James Gurney, creator of the Dinotopia books.

Pigments and their Chemical and artistic properties
Excellent site!
An excellent resource for aspiring portrait artists.  Tutorials, demonstrations.