This is a great, interactive site with art games, hands-on activities and excellent art lessons.
The National Gallery of Art provides a behind-the-scenes look at the planning and construction of Art Nouveau, 1890-1914, with the most comprehensive exhibition ever on the subject.
The Kennedy Center's Arts Edge
The mission of ArtsEdge is to help artists, teachers, and students gain access to and/or share information, resources and ideas that support the arts as a core subject area in K-12 curriculum.
This site has lots of detailed art lessons and activities, many with step-by-step illustrations.
Do you have a question about American art? Specialists at the Smithsonian American Art Museum with answer it for you.
Lots of excellent links
National Endowment for the Arts
The home page for the National Endowment for the Arts