Alvaro Fogassa of Homemade 3D Printer has posted some details about his inexpensive design. We've written on Alvaro's expedition before, and now he tells us how it works, and points us to the software he used.
The Lexmark Z12 inkjet-printer based design involves using common dental plaster as it's material, mixed with a water-based glue and of course, water. At this point his minimum resolution is 2mm, but that's pretty good for this approach.
Alvaro is now off working on a new and larger build chamber (300 x 210 x 125mm). Good Luck!