agTweener provides a toolkit for Silverlight designers and developers to achieve animation and transition effects similar to toolkits currently available for Flash/Flex developers by defining transition effects in .NET code and applying these effects to any FrameworkElement.
The best way to understand what this is all about is to take a look at some samples. The features and techniques to integrate this library into a Silverlight application have been blogged about in these posts:
agTweener is a c# Silverlight library based on the Tweener Actionscript library for Flash/Flex. A preset list of transition functions based on Robert Penner's easing equations is available. The library has now been updated to support Silverlight 2 Beta 2.
The code for all of the samples is also available in the Releases sections.