Popular stencils
Cell Surface Receptors
These are surface receptors that I use for diagrams
puzzle pieces
Various puzzle pieces.
Some basic network components
Various network components from various sources, some I've found useful over the years. I'm new to OmniGraffle, missed these items.
Swim Lanes
This stencil provides basic structure for diagramming using swim lanes, and split swim lanes to show separation of processes of tasks.
Web Sketch Cursors
CSS3 Compliant cursors in a "sketch" style, for mocking up web UX designs. Includes: default, crosshair, pointer, move, text, wait, help, progress, not allowed, vertical text, and several resize arrows.
Database/store
A simple, classic database cylinder.
Neutrik BNC NBB75DFIB chassis mount
Neutrik BNC NBB75DFIB chassis mount with drill order to scale
WindowsPhone 7 Controls
Replication of most of the controls for WindowsPhone 7. Probably could be optimized more but thought I'd share in the current state as it may be useful.
Endian UTM Firewall Features
Endian Firewall Feature Highlights Icons and Network Icons.