...
- Slice your model in Sketchup, e.g. with http://www.cad-addict.com/2009/07/sketchup-plugins-slice-your-model.html
- Export into SVG: http://sliceforms.wordpress.com/2011/04/22/processing-svg-output-from-sketchup/
Ponoko hat hierzu auch ein Tutorial: http://blog.ponoko.com/2010/03/18/creating-laser-cut-3d-forms-super-easily/
OpenSCAD
There's a script to export 2D DXF clices from any OpenSCAD model: http://www.thingiverse.com/thing:9233
OpenSCAD can import STL files, so could be useful for any 3D mesh