Laser cutters are great DIY tools, but they're expensive. If you'd prefer to build your own, Instructables user SilverJimny shows you how using an Arduino.
The build here uses an Arduino along with a lot of parts gathered from eBay. Once you put the whole thing together, it connects to your computer for the drawing program, and you can get right to laser cutting or engraving from there. It's a complicated project, but the end result is a full featured laser cutter for a lot less than the commercial version. If you prefer, you can also buy a kit.
The MicroSlice [Instructables]