Thanks to ianwij for commenting this latest info at the mix09 site, http://visitmix.com/News/For-the-Audience-at-Home 

Microsoft® Silverlight™ 3 SDK Beta 1
http://www.microsoft.com/downloads/details.aspx?displaylang=en&FamilyID=d09b6ecf-9a45-4d99-b752-2a330a937bc4

Microsoft® Silverlight™ 3 Tools Beta 1 for Visual Studio 2008 SP1
http://www.microsoft.com/downloads/details.aspx?displaylang=en&FamilyID=11dc7151-dbd6-4e39-878f-5081863cbb5d