3dpBurner is a open source laser cutter/engraver.
It is created with the same RepRap concept, using 3D printed parts and some easy to find "vitamins" (not printed hadware).
I tried to do it as cheap as possible, by using cheap electronics
and a "low power" laser (a laser diode).
The X/Y working area is fully customizable and the max working object height is up to 50-60mm.
Check http://www.3dpburner.blogspot.com for details.
NOTE: It is imperative you get the apropiate protection for your eyes and prevent the toxic fumes released by the most of materials. First thing you need to buy prior to powering your laser is a pair of glasses adecuated to your laser wave lengh. The laser spot or laser reflections can hurt your eyes very easily. Avoid to use invisible diodes as IR laser diodes, they are more dangerous due you can not see when they are powered.