To quickly visualize an architecture or a structure Visio might be the tool of choice. But to make such a diagram really appealing you have to have the right shapes.

To create diagrams for SharePoint there are a couple of free shapes available. I collected some of these shapes:

• MOSS (2007) Site Strukturen
• Visio Stencils for IT Pro Posters (SharePoint 2007)
• SharePoint Visio Stencils (SharePoint 2010)