I found this to be an interesting free CAD tool.

Anyway if you want to play around with it you can find it here.

http://sketchup.google.com/intl/en/download/gsuwenthankyou.html

and some sample arcade files here.

http://www.arcaderestoration.com/index.asp?OPT=3&CBT=66

I just figured it may come in handy for mocking things up.

I used it when I built my MAME cabinet, and it's pretty good once you get the hang of it.  It's not as powerful as something like SolidWorks or AutoCad, and I actually got a little frustrated with not being able to enter numbers as easily as you can in autocad to get exact measurements (I learned AC as basically a keyboard only app, whereas this is very mouse driven).  Still, you can't beat the price.