Loving it. write code run it anywhere .NET runs no recompile..
The Portable Library Tools is a new Visual Studio add-in from Microsoft that enables you to create C# and Visual Basic libraries that run on a variety of .NET-based platforms without recompilation including: .NET Framework, Silverlight, Windows Phone or XNA project
Requires Visual Studio 2010 SP1

No more complicated build scripts, #defines. Portable libraries enable you to easily share code between apps that target different platforms. Why wasn’t this available years ago..
Things most useful for Silverlight developers:
- ObservableCollection<T> can now be shared between Silverlight and Windows Phone projects, enabling simple ViewModel sharing between those platforms.
- Bootstrapper pre-requisite for Setup and ClickOnce projects. This enables these projects to pre-install .NET 4.0 + KB2468871 on end user machines.
- System.Net types can now be shared between Portable Library and .NET projects.
Download Link:
http://visualstudiogallery.msdn.microsoft.com/b0e0b5e9-e138-410b-ad10-00cb3caf4981/

Thanks to reader Francois Vanderseypen for noticing that posted version wasn’t the final update. I normally write and schedule and deploy updates on a timed basis to this blog.. This one snuck past me..