Ever regret not going to art school? Here's a great little resource that might fill that void. SmartHistory is being developed as an alternative to a art history book. Not just that, it also has a great design and user interface. You can quickly see a sample of images from a certain time period. Below is an excerpt from the Industrial Revolution period. You can also search by artist and medium.
So take a look if you want to beef up your art knowledge: SmArtHistory