I'm trying to do the same thing. I've been looking at the McWire plans on reprap.org. Ideally, I'd like to build this using 1" or 1.5" square pieces & using a dremmel as the cutting tool. The basic frame is pretty simple, I'm not sure how I'd do the z-axis.
http://reprap.org/bin/view/Main/McWi...tesian_Bot_1_2
- Ed