Microsoft has released Microsoft Silverlight 5 RC Tools for Visual Studio 2010 Service Pack 1

This package is an add-on for Visual Studio 2010 Service Pack 1 to provide tooling for Microsoft Silverlight 5 RC and Microsoft WCF RIA Services V1.0 SP2 Preview (April 2011). It can be installed on top of either Visual Studio 2010 Service Pack 1 or Visual Web Developer 2010 Express Service Pack 1. It extends existing Silverlight 4 features and multitargeting capabilities in Visual Studio 2010 Service Pack 1 to also create applications for Silverlight 5 Beta using C# or Visual Basic.

This download will install all components necessary for Silverlight 5 RC and Microsoft WCF RIA Services V1 SP2 Preview (April 2011) development:

Silverlight 5 Beta Developer Runtime
Silverlight 5 Beta SDK (software development kit)
Update for Visual Studio 2010 Service Pack 1 and Visual Web Developer Express 2010 Service Pack 1 (KB2502836)
Microsoft WCF RIA Services V1.0 SP2 Preview (April 2011)

  Microsoft Silverlight 5 RC Tools for Visual Studio 2010 Service Pack 1