DoubleAnimation, DoubleAnimationUsingKeyFrames

1. DoubleAnimation - Uses a From/To direction.
2. DoubleAnimationUsingKeyFrames - This is a container for a set of key frames that will determine the value at a given set of points along a time line. We will look at this option in our next tip of the day. 

http://blogs.silverlight.net/blogs/msnow/archive/2008/12/01/silverlight-tip-of-the-day-76-animating-objects-with-doubleanimation.aspx