Here's some research I did awhile back about 3-D printing that's within reach of private individuals. It certainly isn't the 'best' in the realm of rapid prototyping, (look at companies like Zcorp for that) but there's plenty of potential in both the projects below.
A university project at Cornell produced a 3D printer you assemble yourself, that runs just about 2500 dollars in parts.
http://www.kobask8.com/servlet/Categories?category=Fab@Home sells the finished product, but the website below has all the information you need to build your own.
This particular model uses a mechanically-adjusted syringe. It can precisely control the flow of material, like silicone rubber. Moving in 3 axes, x y and z, it otherwise behaves like a print-head...traveling around to lay down the 'ink', except in this case the 'ink' is a material that gets built up layer by layer to form a 3D shape instead of a 2D image. It can also use a variety of materials, unlike some of the commercial products.
http://www.fabathome.org/wiki/index.php?title=Main_Page is the project's wiki, where you can watch some videos, download plans for the fabber, and find links to the off-the-shelf items you'll need.
It's about the size of a microwave, but the actual build platform isn't quite that large. It would be useless for large items, but smaller ones? No problem.
There is a second, similar project aimed at creating a cheap Fused Deposition Modeler. 'Reprap' is supposed to cost around 400 dollars in parts, and heats plastic (and potentially other materials) before extruding it in layers to build up objects.
http://reprap.org/bin/view/Main/WebHome
It's far less developed than the
fab@home project, and requires more do-it-yourself building from the looks of things...including PIC programming, breadboarding, etc.
