Silverlight 4 Beta - developer release

http://silverlight.net/getstarted/silverlight-4-beta/

"This latest version delivers hundreds of features and controls that, when combined with the continued innovation in Microsoft’s world-class tools for designers and developers — Microsoft Visual Studio and Microsoft Expression Blend – present the leading edge in rapid, powerful application development. With printing support, rich reporting and charting, and integration with back-end systems and server products including Microsoft SharePoint, Silverlight is ready for business."

"IMPORTANT DEVELOPER NOTE:

Visual Studio 2010 can be installed side-by-side with Visual Studio 2008 SP1. For Silverlight 4 development, you will need Visual Studio 2010. Please read the known issue on installing Visual Studio 2010 if you already have the Silverlight 3 SDK installed."

Videos and Samples
http://silverlight.net/learn/videos/silverlight-4-beta-videos/

Silverlight 4 Beta - developer release