Troy Jefferson interned this summer with the WPF team and gathered a bunch of Effects that had been written by members of the WPF team. These are now available for downloading on CodePlex. At that same site, you can also browse to a video of these effects in action.
The single input effects in this library include:
There are also a set of two-input effects package up as "transitions" for doing interesting visual transitions between elements. These include:
Thanks, Troy!