There's some RAMPS CNC machines around, I've been thinking about making one of these: http://www.thingiverse.com/thing:49484

Should be good for light work, routing fiberglass laminate, acrylic, plywood, etc.. I haven't done much research, but I think one of the drawbacks of using a RAMPs to control CNC is that it has lower precision, it moves the spindle in very tiny straight segments, not proper curves; although, IIRC, there has been some work to make the Marlin firmware able to work with curves.