Just out of curiosity, can you point me to a good tutorial or two about designing parts to be printed in 3D by Shapeways? I've got some items I think might be interesting to try, but haven't a clue how to get started.

I am a Linux user and have been fiddling with with FreeCAD a bit, but applying it to the construction of a model of a real part has so far eluded me. I also have the professional version of QCAD available, but I'm pretty sure that's limited to 2D work.

Thanks.
Bill Lugg