First off, IE8 final has launched. Interesting to see if this encourages the corporates to get off of IE6. Doubt it.
Then there is SuperPreview, MS' entry into the IE6/7/8 side by side layout debugging tools.
And finally, YouTube is using SilverLight to live stream the March Madness basketball games. The reason Flash is on so many devices is because of YouTube, and this may well be the transition point to push SilverLight adoption up into the interesting area.