WPF UI Animation Library
There's some effects and transitions libraries on Codeplex.
And this one which lets you transition between different UserControls.
In fact, have a good scout around on Codeplex and CodeProject and you will find several other libraries that may help you out.
Try having a look at Transitionz which is a free open source WPF Animations library published and used by SciChart.
It allows you to animate Opacity, Translate Transform, or Blur on attached property changed, on load, on visibility. With MVVM support allowing changes from a view model.
The Github wiki & source is here: https://github.com/ABTSoftware/SciChart.Wpf.UI/wiki/Transitionz-Library
And NuGet is here: https://www.nuget.org/packages/SciChart.WPF.UI.Transitionz/