The Mvvm Platform for Xamarin.iOS, Xamarin.Android, WindowsPhone, WindowsStore, WPF and Mac. Includes databinding support for Android XML, for iOS XIBs and for MonoTouch.Dialog.
XperiAndri.Interactivity is a set of libraries to perform common tasks faster using Blend Behaviors.
Cimbalino Windows Phone Toolkit
A control toolkit for Windows 8 XAML applications. Contains some UI controls to make it easier to create Windows UI style apps for the Windows Store in accordance with Windows UI guidelines.