Our students often respond to visual images (especially from popular culture), but there are lots of classical artistic images that can be useful as well.
The Web Gallery of Art has hundreds of images from paintings and drawings, including classics such as David's Death of Socrates and Raphael's the School of Athens.
Plato's Cave. TΦ101 has not been able to find a satisfactory diagram of Plato's cave anywhere on the Internet. Now, Margaux LaPointe has produced a sketch of the cave that is accurate and helpful.
Artistic images of the life of St. Augustine. Augustine's Confessions isn't done in too many intro courses, but this site illustrates and narrates scenes from his life using the frescoes by Gozzoli at St. Augustine's church in San Gimignano, Italy, and the stained glass windows in the St. Thomas of Villanova Church on the campus of Villanova University. An instructor's guide provides some ways to use the material in classes.
Graphing the History of Philosophy: This stunning diagram visualizes the links between various philosophers and their influences.
Update: 17 Dec. 2015 (E. Tarver)