I've just started building my CNC foam cutter.
Step-by-step progress is being recorded at http://www.homecnc.org/index.php/Cheap_Foam_Cutter
My objective here is to build a fairly cheap machine that's buildable with the tools I have (meaning, no drill press, no lathe )
Hopefully, the page above will be useable as a step-by-step guide for easily building a cutter.
My background is in software, so this real world stuff is a bit of novelty at the moment
I have all the electronics, and have cut the wood so the next step is to start assembly....
My cost to date is around $USD330, most of which is the stepper controller board.
Many pictures at the wiki page above.