SmoothHD

Akamai / IIS7 / SilverLight 2.0 / VC-1 == HD over broadband happiness.  It's sort of cool - the video started off a tad blurry and then got sharper after a few seconds and I didn't have a single glitch. 
Pretty impressive stuff: http://www.smoothhd.com/
Also see: http://www.akamai.com/smoothhd