I've used my Sony PlayStation Eye with several desktop apps. Why doesn't iChat see it?
I have a Sony PlayStation Eye USB camera and microphone.
I have successfully used it on my Mac Pro desktop with several video application (iShowU HD for example).
However, although iChat will recognise the microphone it will not work with the camera, see screen shot.
See http://webcam-osx.sourceforge.net/ Good luck! :-)