There are two distinct visualizations — actually three, since one of the visualizations is really a two-for-one. That’s the “network” view. It gives a grid on the left, mapping out the intersections between characters, and a sort of three-dimensional node map on the right. Move your mouse over either and observe the results!
This view, for my money, is the more difficult to use and understand, but take a look at the “stream” view (part of which is pictured above). In this two-dimensional view, the books of The Iliad are laid out horizontally (scroll with the mouse), with parallel streams representing the major characters. As in a word-cloud, the larger a character’s name, the more prominent his role at each point in the poem. It’s a little bit like the classic xkcd representation of The Lord of the Rings (if you haven’t seen it, follow this link; and note: it’s the film version).
Fascinating, eh? I think these sorts of creative visualizations can really help students grasp the complexity of expansive literary works like those of Homer, Virgil, and Tolkien.
Note: The visualizations use the HTML5 <canvas> element, so you’ll need a browser capable of rendering it. That’s most of them, but with the conspicuous exception of any version of Internet Explorer except the latest (version 9).