"This site gives a history of art, worldwide. It contains biographical and societal information on the artists when available. It has examples of the art pieces (since the website is sponsored by a museum, it has many of the pieces itself), with time and place of origin, the owners name, and the fabric/material it is made of. It separates topics by country/empires."
MIT Open Courseware offers an extensive series of online courses from their Architecture department. Courses generally include lecture videos, assignments, exams, and more.
Art History @ Saylor