Microsoft® Silverlight™ 3 Tools Beta 1 can be installed on top of either Visual Studio 2008 SP1 or Visual Web Developer 2008 Express with SP1, and it provides a Silverlight project system for developing Silverlight applications using C# or Visual Basic.
Install Microsoft Silverlight 3 Tools Beta 1 for Visual Studio 2008 SP1 >> Silverlight3_Tools.exe: Add-on for Visual Studio 2008 SP1 for developing Silverlight 3 applications
Install Microsoft Silverlight 3 SDK Beta 1 >> silverlight_sdk.exe: Development Kit provides libraries and tools for developing Silverlight applications.
The Microsoft Silverlight 3 beta runtime