projectM - projectM is an LGPL'ed reimplementation of Milkdrop under OpenGL.
Visualify - Visualize your top artists on Spotify
Magic Music Visuals - Fully-customizable and highly responsive visuals for live and recorded audio & MIDI.
Spotify Web Visualizer - Beautiful full screen visuals for Spotify web player
Kauna - Kauna is a music visualizer. Kauna renders any sound reproduction in system.
Graphic Foundry - High-impact audio reactive music visualizers 💎