There is an avatar feature that comes with the Logitech Quickcam Pro 5000, and some of their other models. It allows you to send out your stream with various things superimposed over you such as sunglasses, a cowboy hat, rabbit ears, arrow through the head, etc. They follow the locations of specific points on your face very well to where it really is realistic with the mouth and eyebrow movements, the people I have shown it to have reacted uproariously, even the techno-jaded. You don't have to have one to receive the stream of course.

Check out the avatars
here and
here.