If you need a Raspberry Pi Model B drawing in the DXF format (might work with Model A, too. I didn’t check), you can download it from here. It contains some component outlines as well as screw holes.
Raspberry Pi DXF
Since Arduino Uno and Mega DXF drawings are hard to find (I didn’t find any for the Mega board), I created my own and I am sharing them here with everybody. These are saved in the AutoCAD 2007 DXF format. Enjoy!