This is a home laser show I built with a 35mW green lab laser. The laser bounces off a mirror attached to a speaker, then goes through a diffraction grating so the patterns will cover my entire ceiling. It's pretty sweet.
You'll need a green lab style laser module, a pair of old headphones, a box, a switch, an AC/DC adapter, and some hand tools.
Here's a link to more detailed instructions with a full parts list
You can see some videos of it in action here