The 3 main parts of Silverlight are (according to Ray Ozzie):

1. Video, High-quality animation or performance
2. .Net, Developer/designer productivity or skills reuse
3. Streaming, Broad audio/video reach or low cost of delivery

There’s also a Silverlight Community Site at http://www.silverlight.net where you can see demos, get some samples and/or participate in the discussion on the forums.

Silverlight 1.1 alpha comes with support for .NET (you can use C# or VB.NET) as well as support for Ruby, Python and Managed Jscript.

Some more info about Expression:

• Expression Web 
• Expression Blend
• Expression Design
• Expression Media
  • Expression Media Reader 
  • Expression Media Encoder

Microsoft ASP.NET Futures (May 2007)

The Microsoft ASP.NET Futures May 2007 (“Futures”) release contains an early developer preview of features providing a wide range of new functionality for both ASP.NET and Silverlight™. The functionality in the Futures release includes early experimental versions of features currently being considered for future versions of ASP.NET and the .NET Framework. The Futures releases assume prior knowledge of the core features of ASP.NET including the previous ASP.NET AJAX Futures January CTP.

Features in this release include ASP.NET Silverlight server controls, new functionality for ASP.NET AJAX Extensions, dynamic data controls, enhancements to dynamic languages, and more.

Download ASP.Net Futures

Some more Silverlight downloads: http://msdn2.microsoft.com/en-us/asp.net/bb187452.aspx

• SilverLight Streaming Service
• SilverLight Streaming Service SDK