YSK Butterchurn Visualizer is a web-based version of the Milkdrop visualizer from WinAmp with an attached media player (butterchurnviz.com)
It will play local files, SoundCloud files or you can just have it listen to the music you’re listening to via your microphone and do visualizations based on that. It does all three very well. Some of the visualizations I’ve seen would have made me believe in magic back when I was using Milkdrop.
