I have been thinking about this project and gathering parts for some time and I think I am ready to start building. Up until now the biggest road block was software but Printrun has a projector mode that works with skeinforge's craft output.
DLP Engine:
I plan on using a dlp engine from a dlp tv that was broken on craigs list. This should give me a larger print area than with a projector.
Electonics:
I am using an Arduino nano with teacup firmware loaded and a hobbycnc steper driver. The stepper driver has a blown X and Y but the Z and A still works which is all I need.
Materials:
1/2-10 acme lead screw
2x 18" 20mm linear rail
I am using corian since i have a ton laying around but plywood or MDF should work.
The opening in the base is 12"x9" and the frame is 18" tall so I should get 14"-15" of z.