I know everyone and their sister will be blogging this today so sorry if you've already read this a bagillion times. Scott Guthrie has the details here. The coolest thing is that we are officially endorsing the Moonlight project so that:
"we are announcing a formal partnership with Novell to provide a great Silverlight implementation for Linux. Microsoft will be delivering Silverlight Media Codecs for Linux, and Novell will be building a 100% compatible Silverlight runtime implementation called 'Moonlight'.
If you originally installed the Silverlight RC, then you should already have the RTW update (due to auto updating). However, the 1.1 bits DO NOT auto update. You should install the latest 1.1 bits from here. To figure out what version you have, just right click any Silverlight content and select "Silverlight Configuration."
1.0 RTW = 1.0.20816.0
Latest 1.1 Refresh = 1.1.20816.0
Also, check out www.silverlight.net for links to some of our launch partners sites to see what they've done with Silverlight (HSN, WWE, AOL, Halo 3 on MSN, MLB, and more).