Quote Originally Posted by Yora View Post
Hydrogen, carbon, nitrogen, and oxygen are the main component of all living things on Earth, precisely because they are available in the air. (Even all the water on surface of the Earth is there because it condensed out of the air and fell to the ground.)

Sugar, starch, fat, alcohol, cellulose and lignin (that is wood), chitin, methane, propane, butane; ammonium, nitrate, nitroglycerin, TNT, and ANFO are all different combinations of these four elements. They offer you more options than probably any other four elements.
And let's not forget modern carbon-based materials like nanotubes, which you can weave into many useful and durable things. Even making current conductors is not a problem, as graphene is entirely within possibility along with a whole family of polymers which can conduct like metals of semiconductors.

Also diamonds, if you need something really sturdy.