Microsoft released the Silverlight 4 Tools for Visual Studio 2010 and WCF RIA Services. If you already have Visual Studio 2010 installed (or free Visual Web Developer 2010 Express), then you can install both the Silverlight 4 Tooling Support as well as WCF RIA Services support by downloading and running this setup package (note: please make sure to uninstall the preview release of the Silverlight 4 Tools for VS 2010 if you’ve previously installed that). This package is an add-on for Visual Studio 2010 to provide tooling for Microsoft Silverlight 4 and RIA Services. It can be installed on top of either Visual Studio 2010 or Visual Web Developer 2010 Express. It extends existing Silverlight 3 features and multitargeting capabilities in Visual Studio 2010 to also create applications for Silverlight 4 using C# or Visual Basic.
You can see all of the above Silverlight 4 Tools for Visual Studio 2010 features (and some more cool ones I haven’t mentioned) demonstrated in action:
More Info: Download