If you use my Cinch MVVM framework I have some news.
I have just down a new update to improve several areas, and have also added some extra helper classes.
Here is a breakdown of what has been added/changed
1. Resynced with MefedMVVM version 75221
2. Added GenericRule class, which means no more casting inside rule class
3. Added Validator class, which can be used as stand alone validator class when you do not wish to (or can not) inherit from the Cinch validating base ViewModels/Models
4. Added new ViewModel interface IViewStatusAwareWindowInjectionAware, to allow WPFUIVisualizerService service to inject full IViewAwareStatusWindow into popup ViewModel
5. Added WeakDelegateReference class, does what it says really
6. Altered WPFUIVisualizerService to fix this issue : http://cinch.codeplex.com/discussions/263365
7. Added AsyncHost (WPF Only) (read the comments at top of this file to see example usage)
8. Added CircularProgressBar (WPF Only)
9. Added AsyncFailedUserControl (WPF Only)
10. Added AsyncBusyUserControl (WPF Only)