If you want a 3D representation of something look to the entire field of Rapid Prototyping. There are a number of companies, such as Stratus and 3Ds for commercial systems, that produce machine that can create objects out of an amazing number of materials to suit your needs. The process is also called additive since it places materials where you want something as opposed to subtractive in that you remove materials, such as a mill would do. The process is not the cheapest and is certainly not for a large production run but it is great for one ofs, custom work, or testing ideas. I have seen it used to build a piece that was no longer available.
The materials used can be anything from a selection of plastics, such as ABS (think Lego bricks) to polymers (saw a piece used to make dentures from a custom shop), to thinks like nylon, and even metals. I believe Nike was even using the technology to make custom running shoes (they would be expensive) and there has recently been a few clothing designers that have even used it to create clothes used in fashion shows (You can be sure that the dress is indeed custom for that person and made exactly made to measure.).
So along with the ability to create anything there is also the ability to scan anything to me able to use it as a model for the prototyping. The machine you use has some constraints on the resolution and the size, and the bigger the object you want the more the machine will cost. There are also experiments in using 3D printers to build things like a house or other large buildings, although the resolution is not the same as for a smaller printer.
Richard