More input on the CAD question from Paul (no surname...):

http://www.opencascade.org/

http://www.tech.oru.se/cad/varkon

http://www.tech-edv.co.at/lunix/MODlinks.html

The problem with OpenCascade may be the same as that for BRLCAD - namely that it's a good geometry engine but needs a user interface. The other two links look useful.

And from Sven Johnson there's:

http://www.openarchitect3d.org

http://www.openfx.org/ and

http://www.ppmodeler.com/


And some more neat stuff from Vik Olliver, this time on electrical conductors interfacing with chips. To quote him:

"I wondered if it might be practical to lay down one layer of relatively soft plastic such as EVA, which only needs to be in the places that will be occupied by tracks. A conductive silver paint pen:

http://www.dse.co.nz/cgi-bin/dse.storefront/en/product/N5184

is then run across the tracks. The layer is allowed to cure, and is covered with another protective layer of softer plastic. The board substrate is then printed over the top of the tracks, with holes left where component legs are expected to go.

"Once the board is peeled off the base platform (or a very thin non-conductive layer of platform protectant such as PVC film might be used as the first layer), components can be pushed through the face bearing the tracks, forming a contact between the trapped conductive layer and the component legs.

"The paint also has applications for printing non-durable switch contacts, though a conductive elastomer might be more appropriate.

"Printing the track in plastic first reduces the dependence on the size of the paint pen tip for track width.

I suspect that it might be possible to print a simple digital circuit such as a calculator/PDA using a PIC, printed keyboard, and a serial LCD for the display - all in a snap-fit case."