I have been building up a set of LDRAW parts for Vex. The first bundle is now available at
HobbyVex CAD along with a preliminary version of the first robot model and instructions at
HobbyVex Robots
The HobbyVex CAD project is based completely on the FREE tools from the LDRAW.org package. Given that people are intermingling Vex and Lego, using the LDRAW tools has a singular advantage that all the Lego parts are already defined. The tools in the LDRAW.org package include a simple way to produce rough building instruction images and also a more complex way to produce professional quality building instructions.
I hope the Vex community will be interested in producing building instructions for the many robots already out there. I'm willing to help where I can; right now I'm working on getting the rest of the parts library converted over.