macam is a driver for USB webcams on Mac OS X. It allows hundreds of USB webcams to be used by many Mac OS X video-aware applications. The aim is to support as many webcams as possible.
In addition, macam also supports downloading of images from some dual-mode cameras. macam especially tries to support those cameras not supported by Apple or by their manufacturers.
macam consist of an application and a component. Run the macam application to verify whether your camera works with your Mac and your USB setup. The component is the actual driver that allows other applications to access the video-stream. (note: iChat does not recognize most USB webcams unless you install iChatUSBCam - this is shareware unrelated to macam)
Many thanks to the spca5xx/gspca Linux webcam driver project, especially Michel Xhaard and friends. Their hard work and helpfulness have made many of the recent advances possible.
If you have a camera and Mac OS X, please help out by testing and reporting the results. Thanks!