I was messing around with some of the animation features in WPF, and here is a simple application (click here to run) that displays animated zooming circles when you click inside the window:
The animation itself is based on keyframes defined in a XAML file. I store the effect as a Resource, so I am able to reuse the animation as many times as necessary. I explain how to do access a resource using code here: http://blog.kirupa.com/?p=56
You can download the source files (XAML + C#) by clicking here.