I've been prototyping some of my ideas using polymorph thermosetting plastic but would like to try and instantiate them into reality a little more professionally, using the new 'democratisation of manufacturing' technology, 3D printing...to this end, can anyone tell me where I can download 3D design software that is compatible with the shapeways machines that a) won't break the bank and b) won't do anything nasty to my computer..?