There are plenty of established ways to get a three-dimensional structure made. Many people beat on metal for days with hammers and dowels, some spend huge amounts of time massaging wooden panels and strips while still others create elaborate molds for fiberglass or even carbon fiber. Is there an easier way? If so, why do you care?
There are many reasons to create a three-dimensional structure. A few that come to mind that have a "green-transportation" purpose are for creating devices to cheat the wind like a bicycle fairing or an automotive body appendage. Here is an instructable which shows you just how to create such a fairing for your bike using some plastic sheeting and a few other miscellaneous items. The author also claims that he is working on a "wind-powered bicycle" which sounds rather interesting.