By popular request, we have packed up and created a download for the stencils that we used to create many of the SharePoint Technical Diagrams. These models are created using Office Visio 2007. You can modify the Visio files to illustrate how you plan to incorporate Microsoft SharePoint Products and Technologies in your own environment.
Here's the URL for the download package: http://www.microsoft.com/downloads/details.aspx?displaylang=en&FamilyID=08105458-1d92-44ad-b7e0-744aa853a7bf.
Let us know what you think.