MilkDrop - 3D audio visualization plugin, compatible with WinAmp plugin API
MasterpieceVR - Powerful VR sculpting & painting tool
projectM - projectM is an LGPL'ed reimplementation of Milkdrop under OpenGL.
Snap Art - Snap's augmented reality platform
Magic Music Visuals - Fully-customizable and highly responsive visuals for live and recorded audio & MIDI.
A-Painter - Paint in VR in your Browser