Build a 3D printer for £300

Researchers at the University of Bath have developed a low-cost 3D printer which can create plastic objects designed on a PC.  Story here:
http://www.reghardware.co.uk/2008/06/04/reprap_machine/

The software is FOSS, and they have set up a website to help people source the components.  The original story suggests that the RepRap as it's called can reproduce itself.  There's a bit of journalistic licence going there.  It can definitely make many of it's own components, but there is still the electronics, and assembly of course.  People are also working on plywood built versions which may be easier to construct.

It's interesting to see how the quality of the components produced by the machines have improved over time:
http://www.reprap.org/bin/view/Main/ItemsMade

The site is quite slow to load as I write, but that may because of traffic generated by the publicity.