Microsoft Silverlight is a cross-browser, cross-platform, and cross-device plug-in for delivering the next generation of .NET based media experiences and rich interactive applications for the Web. Silverlight 2.0 Beta 2 is release, you can start on Beta 2 by

1. Install Visual Studio 2008 then Install Silverlight Tools Beta 2 for Visual Studio 2008
   This add-on to Visual Studio 2008 allows you to use .NET to create Silverlight 2 Beta 2 Web sites. The Silverlight 2 Beta 2 Runtime and the Silverlight 2 Beta 2 SDK are installed as part of this install. For additional information read the overview.
2. Install Expression Blend 2.5 June 2008 Preview
   This is a preview version of Expression Blend for designing Silverlight 2 experiences.
3. Install Deep Zoom Composer
   This tool allows you to prepare you images for use with the Deep Zoom feature in Silverlight 2.

Learn more about Silverlight - http://silverlight.net/GetStarted/ 

Read about the differences and breaking changes between Silverlight 2 Beta 1 and Beta 2 - What's Different in Beta 2