Yahoo! Japan (Japan’s #1 website by unique users and brand impact) demoed a killer UX concept today using Silverlight, a visualization front end for search and tail content that otherwise is hard to navigate/discover across their massive content repository.  Very creative UI concepts, and great integration of some of Silverlight 2’s killer features such as DeepZoom and high def videos.  A video of the demo is posted online:

http://www.microsoft.com/japan/products/expression/creatorsEX/gallery_y.html