RepRap (or the REPlicating RAPid Prototyper) is essentially a 3-d printer, which can replicate many of the parts (around 60%) to make itself. Developed by genius types at Bath University, currently it prints layers of plastic to create the three dimensional item you require, limited only by the size of the machine. Its also open-source technology and open-source software, which means it’s free (apart from the non-plastic parts you would need to buy).
To buy a REPRAP retail they reckon would be £2-300. Or you could build it – they give you the instructions and a list of needed materials.
Think of something you use that is plastic – from a replacement coathook, emergency washer, shelf bracket, leg for your specs – reprap can be configured to make it.
It is an amazing peice of technology, and future plans are to develop ways of using different materials – form ceramics to metals. Checkout REPRAP here.