YouTube has a very cool visualization that lets you discover related videos. Just go to a YouTube video, click on the full-screen button and then click on the small button that shows a network. A lot of video ballons will pop up and the configuration will change once you hover over a button. It's an interesting way to discover videos and it reminds me of visualization sites like
Liveplasma and
Musicovery.
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Update: You can find the visualizations at
www.youtube.com/warp_speed.