Otherfoot: Only Pen and Paper Required [via mefi projects] A concise ruleset for a DIY Roll-Your-Own kind of Apples-To-Apples type game.
DIY Portal Gun on flickr, with a few other pictures and build notes. You want of your own, you can either contact this guy or just ask Aperture about working at their test facilities.
Want to make your own ocarina? Fair enough; a bit of clay goes a long way. But the legends say that only a true master can construct them out of broccoli or carrots.