I discovered this link through today's post on Two Coats of Paint:
Here's an excerpt from their "About" page:
Why We Made Smarthistory
We are dissatisfied with the large expensive art history textbook. We find that they are difficult for many students, contain too many images, and just are not particularly engaging. In addition, we find the web resources developed by publishers to be woefully uncreative. We had developed quite a bit of content for our online Western art history courses and we had also created many podcasts, and a few screencasts for our Smarthistory blog. So, it finally occurred to us, why not use the personal voice that we use when we teach online, along with the multimedia we had already created for our blog and for our courses, to create a more engaging "web-book" that could be used in conjunction with art history survey courses. We also realized that this content would be useful to museum visitors and other informal learners. We are committed to joining the growing number of teachers who make their content freely available on the web.