Free Software For 'Nested Shape Determination'?

This one is for those of you who deal in fabrication...jabber asks: "I'm looking for some free and open software that would do 2D 'shape nesting'. If you needed to cut some shapes out of a flat plane of material, for example, how could you arrange the shapes on the material to get the most useful area (and the least amount of wasted material)? Shape Nesting is used for sheet and slab metal cutting, vinyl sign making, and can even be applied to quilting. There are other features to consider like grain direction (in the case of cutting shapes in wood), and variable sizing (since some applications can allow one side of the flat plane to vary), and minimum distance between shapes (since torch-cutting tends to destroy more material than a laser, for example). I'm sure that software like this exists, and I've seen expensive proprietary applications in CAD/CAM, but is there anything available freely? I prefer source-code, since I could then add any of the features that are missing. Any ideas?"