The Metropolitan Museum of Art hosts 372 art history books online. All of the books can be read online or downloaded as PDFs (warning, some of them are massive files). You can search through the catalog of books by thematic category, format, and publication type. And, of course, you can search through the books by title, author, and keyword.

smARThistory.org is a free multi-media web-book designed as a dynamic enhancement (or even substitute) for the traditional and static art history textbook. The combination of video lessons, text articles, and audio lessons about eras and themes in art history is what makes Smarthistory a valuable resource.