Instructable of the Day:
2W Arduino Laser Engraver/Cutter
This is a super simple and cheap laser cutter/engraver.. it really could not be any simpler..
Raster images with 256 levels of grey .. nope
Autofocus or z axis.. nope
Higher power for metal.. nope
But you load materials and it will give you an image, I think it's pretty impressive for the time invested. Also it seems like a good starting point to add those other features as you go..
It's no GlowForge but it works good for what it is..