Ivtv devices (cx23415, cx23416)
The ivtv devices have built-in hardware compression. They include the Hauppage PVR-150, 250, 350, and 500 cards; for a full list, see supported hardware.
Since the ivtv devices have their own wiki, there is no need to duplicate the effort here.
However, note that the ivtv code has now been merged into the v4l tree in the mainline linux kernel (as of Winter 2007).