TransitioningContentControl

Taken from Silverlight (specifically this port), TransitioningContentControl is great for switching content smoothly around. At it’s core, TransitioningContentControl is a ContentControl, so only one child element can be displayed at a time. When you change the content, an animation is played switching the two.

<Controls:TransitioningContentControl x:Name="transitioning" Width="150" Height="50" Transition="DownTransition" />

Built in there are several transitions:

Default
Down
Up
Right
Left
RightReplace
LeftReplace
Custom