I just came across this demo for real-time 3D video effects that can be used with the Logitech QuickCam web camera. It is quite impressive - I remember seeing similar technology as cutting-edge computer graphics research only a few years ago. It doesn't seem ultra-robust, but good enough for having fun at least.
Together with voice changers, it kinda solves the non-anonimity problem of webcams and microphones.
Check it out, and think of Microsoft's upcoming camera, and Sony's EyeToy 2.
(The official info from Logitech on these effects can be found here.)