I am finishing by second hobby CNC router build - although I'm not sure a project like this is ever finished. I started with the excellent tutorials on buildyourcnc.com.
For a plywood machine, I am amazed at the accuracy. I have been able to do isolation PC board milling with excellent results. I have taken great pains to document every step with images and Google Sketchup drawings. If you are planning to build your own machine, give it a look. woodworkerbcncrouterproject.blogspot.com