Visualization of networks has been something that I've been watching for some time and have yet to see anything that looks really interesting. Many vendors use the Tom Sawyer Software package. Netviz had an interesting package but CA (which acquired them via their Concord acquisition) decided to shutdown their operation - it only generated $4M in revenue to a $1B operation.
Routing Visualizaton
The problem I've seen with visualization is that it doesn't scale to networks that have more than about 50 or 100 routers. Routers tend to be a harder problem than switches because the interconnections are more arbitrary. When you look at a national or global network that has 50 or more remote locations, there isalmost no way to display the routed network in a way that makes sense. One approach is to use hyperbolic display technology, which makes the view look like that through a fish-eye lens. A spin-out from Xerox Parc, called Inxight, has been developing some interesting visualizations, such as the one below.
Switching Visualization
Switched networks that rely on spanning tree can be more easily visualized because of the directed graph that results from the spanning tree protocol. Sure, there may be some complications due to backup links, but switched networks tend to be much smaller in scope than routed networks, which makes the visualization problem much easier to solve.
If you're aware of interesting, novel, or useful visualization techniques or products, please add a comment so I can check them out.
-Terry