To build a laser oscilloscope you'll need five basic parts: a cat toy (laser pointer), a speaker with a mirror fastened to its cone, a sound source (I used a tone generator on my iPod touch), a spinning mirror, and a target screen:

How you choose to build it is really up to you (depending on what materials you have on hand). I chose to use Snap Circuits and construction toys because they don't require power tools, or a soldering iron to construct them.