Luz is a music visualisation studio for VJs and creative couch potatoes.

Luz lets you produce beautiful, moving 2D vector graphics environments mixed with live drawing and other live inputs. Any aspects or behaviors can be made to animate with the beat or other aspects of the music.

The Luz Studio lets you create effects and assign inputs from MIDI and computer keyboards, Wiimotes, Joysticks and Gamepads, Wacom tablets, and other input devices.

Luz is Free Software and costs $0.
Read more at the project page.