A handy set of isometric icons based on Visio's icons.
Stencil of additional Apple hardware and misc. networking components. Excellent for creating physical diagrams.
Stencils for QLogic Fibre Switches
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.
Collection of hosts, clients and assorted support.
The MacADSL team has designed a network stencil that can be used to draw networks in a comprehensive way with few colors in order to generate small image files to be published on the web.
The following picture shows an OmniGraffle palette I put together for doing network diagrams. It may be useful for others.
Firewalls, VPNs, etc.
WLANs, RF, etc.