Film & TV stencils
Free
XRackPro2
XRackPro2 Omni Graffle Stencil for 4U, 6U, 12U and 25U Noise Reduction Enclosure, Noise Reducing Server Racks in Platinum and Black.
Free
Yamaha Design
This is what I use to design small sound systems connection and setups. Yes, I'll do the color version soon.
Free
Zouzie's Broadcast Collection #1
Some cameras plus other TV and film industry items.