I have created a SketchUp model for the UNO Rev. 3
The attached PDF file contains a 1:1 drawing you can print and use to help space things out in your projects.
I am also including the .skp file that you can import into “SketchUp Make” and use it in your designs.
http://www.sketchup.com/download
Please confirm the drawing dimensions to your UNO PCB prior to drilling etc.
If you visit “SketchUp 3D warehouse”, there are models much better than my version.
You can find other versions of Arduino PCBs some motors, components, etc.
Enjoy.
Edit:
I use drawings like this to make sure everything fits in a case before I commit to drill holes.
UNO Rev 3.pdf (13.2 KB)
UNO Rev 3.zip (83.3 KB)