So you read articles how 3D printing will be a new revolution and you wonder how it can do anything for you. I came across this nice site where a car enthusiast is building an Astin Martin DB4 with 4x4 inch squares of plastic printed in a 3D printer here.
If I'm understanding his process he will assemble these small components with a framework behind it to hold it together, sand and fill the gaps, and then use these panels to create fiberglass molds for the final body. Doing it this way has cut his manufacturing cost by 1/4. It's still early in the process but 70% of the body is done already. Imagine being able to print your own repair panels for your car after a crash? Better yet - download someone's plans to modify your car's body.