I've found a few that work by searching these forums. Look in the OSX and peripherals sections for USB and webcam with OSX.
I have a TouCam, from Phillips that works with the drivers from a resourceful German programmer who modified the PC-Linux drivers to work for OSX. It works quite well, although not ALL features work.
Good luck and you can find the links and answers in these forums. I don't remember them offhand.