The modular car is an automobile that you can design yourself.

Dutch designer Marijn van der Poll would provide a blank canvas of a car, with the fundamentals of chassis, engine and the rest simply surrounded by a cube of polyurethane foam (the same material used for surfboards).
People would have to go at the cube with a saw and a piece of sandpaper to attain their desired shape, then take it to a body-shop to be laminated in glassfibre and polyester resin. (more images in Vivid)

Marijn van der Poll recently collaborated with Marcel Wanders for the most famous version of the modular car: it was showned at the last Salone del Mobile in Milan and covered by Bisazza in mosaic. (images and on flickr)