I just came back from BUILD where I gave a talk about a new .NET profile that managed developers will be using when writing Windows 8 Metro style apps. You can watch the video at https://channel9.msdn.com/Events/BUILD/BUILD2011/TOOL-930C
We just released the official version of the Portable Library Tools. The set of tools and updates to .net platform allow you to create dlls that can be used in .NET Framework, Silverlight, Windows Phone, and XBOX projects. You can download the tools here and read more about them on MSDN.