Urmusic is a fun browser app to create and share your own music visualizers, easily and for free, using the latest HTML5 features, such as canvas, Web Audio API, and MediaRecorder.
Press F1 to toggle the interface.
This app works better with Firefox.
I recommend using it because some features aren't available on other browsers.
Example: You won't be able to drag and drop a song on some browsers. Streaming from SoundCloud should still be possible though.