I have just finished creating what I think is a rather nice TimeLine Control.
Here is a video of it in action
It is capable of displaying dates as different states. It has the following viewing states:
It supports friction enabled panning if there is to much horizontal data to view. it uses the lovely Transitionals WPF dll from codeplex, to transition between views. This is quite a complex control and is a good example (at least I think so anyway) of how to use the state pattern to create more workable complex UIs.
I also feel it is quite ease to use and fairly customisable if you do not like my default look and feel.
And here is a link to a proper write up about the code and which also includes the source code and a small demo project :