I’m sure he’s not the first to make objects with cast shadows, but Larry Kagan uses steel wire and light to project some interesting artwork. There is a video you can watch at his site, and there is also a gallery with some pieces that he has done. I find this interesting because it uses a three-dimensional form and transposes it into a flat form. Normally people try to mimic 3d imagery on a flat surface, and he is doing the opposite. I like what he says: “the shadow isn’t just a line on the wall, but it’s really a volume in space…”