Other
Tfao: American Impressionism to Modernism
This site gives a breif history of art movements from Impressionism to Modernism, concentrating in America. There are also pages linked to key artists within each movement where you can also see their work.
ibiblio
Ibiblio: Web Museum: Futurism
Describes exactly how the Futurist artistic movement was initiated. Discusses the celebration of change in art during the 20th century. Includes a brief French translation.