This is a nice set of objects and assets to better manage projects in Apple's DVD Studio Pro. Also available in a small version.
WLANs, RF, etc.
Voice, VoIP and other related devices.
Group of conceptual and functional icons.
Firewalls, VPNs, etc.
Various types of probes and management hosts.
Collection of hosts, clients and assorted support.
Additional UML diagram tools, esp. for Use Case and Activity diagrams. There is also a Domain object for class domain or namespace groupings in Class and Collaboration diagrams.
Falk Stern took a set of the basic Cisco router and switch icons for Visio and created a handy OmniGraffle stencil set out of them. Firewalls, routers, switches and even the ubiquitous internet cloud are all available.