Xamarin has launched the Xamarin Designer for Android that is now available for Visual Studio and MonoDevelop. The Designer allows to visually create beautiful layouts for Android applications from directly within Visual Studio and MonoDevelop.
[youtube duKyuaYK8RU]
News source: http://blog.xamarin.com/2012/05/14/xamarin-designer-for-android-available-for-visual-studio-and-monodevelop/