I needed to create a network diagram which included virtual machines. I found these icons to distinguish between physical and virtual servers.
![image image](http://lh3.ggpht.com/_ZVOaTjILAbU/TRn_9lzjosI/AAAAAAAAIDU/CPVaClSls6U/image_thumb%5B1%5D.png?imgmax=800)
http://www.vmguru.com/files/Virtualization_2k3.zip
There are more icons available here.
http://www.visguy.com/2008/05/27/virtualization-visualization-with-visio/Etiketter: Visio