Would you like to build a CO2 laser cutter similar to this?

That can cut things like this:

Instructables has an exceptional step-by-step guide as to how to go about it.

As the introduction states:

The general idea of this CO2 laser system is that a beam is directed down to a part for cutting. The part sits on a computer controlled platform which moves the piece around the stationary laser beam. Cutting is acheived (sic) by passing the beam through a focusing lens. A focused beam exits through the bottom of a cutting head nozzle. Gas, such as oxygen, is fed into the side of the chamber below the focusing lens. This gas exits the nozzle along with the beam and the laser beam/oxygen combination serves to vaporize the steel for cutting.

There are pictures a plenty, videos of it in action, a block diagram pdf and seven extensive pages of instructions on how to build one.

Well, the site is called Instructables.