http://www.freeship.org/ Cool free software to make ship hull designs - includes unfolding *** http://papercut.sourceforge.net/ Nifty paper-shape thingy ... fun projects for the kids? *** http://sourceforge.net/projects/brlcad The CAD software used by the Military! -taken from their website: "In 1979, the U.S. Army Ballistic Research Laboratory (BRL) (now the U.S. Army Research Laboratory [ARL]) expressed a need for tools that could assist with the computer simulation and engineering analysis of combat vehicle systems and environments. When no existing computer-aided design (CAD) package was found to be adequate for this purpose, BRL software developers began assembling a suite of utilities capable of interactively displaying, editing, and interrogating geometric models. This suite became known as BRL-CAD."