Interested in learning more about a specific artist or art movement? Artcylopedia is an excellent (and free!) place to begin! My favorite part of the site is that you can browse artists by a number of categories, including alphabetically by name, medium, and nationality.
Artcyclopedia also includes art news from around the world, which is updated nearly daily and spans a wide range of periodicals. Over 9000 artists and 2900 art-related sites are included!