Hack-A-Day, a homebrew/DIY/hacker blog, has been home to a couple of make-it-yourself CNC projects including a CNC laser cutter and a (somewhat less useful but demonstrative) CNC Etch-a-Sketch. Now they have a pretty active thread in their forum discussing the how-to of home CNC. It’s worth a look.
DIY CNC Thread [Hack-a-Day Forums]
Update: Another Homebuilt CNC Table [via Hack-A-Day]