I saw that several months ago, during the summer. Anybody who visits that site should realize: it's a fun project that will work, but you may lose your sight in the process.
At the intensity of that beam, reflections off traditionally non-reflective objects can blind you (for instance, the skin of a balloon) - and these reflections are next to impossible to predict or control in a handheld unit. There is a reason high powered lasers in academia are anchored to expensive optical benches and are directed with mirrors approaching 100% reflectivity... to control these kinds of reflections.
So, to all DIY Head-fi-er's out there that read this: remember the laser scientist's maxim - "Do not look into the beam with your remaining good eye." This could be you, if you decide to undertake this project...
(hypocritical note: I am considering building one of these myself, but would make certain that I knew the exact wavelength of the beam and purchased laser goggles eliminating that wavelength. Also, I would not use it around any other people unless they also had goggles.)
