OK...so it still doesn't work out-of-the-box. I've determined that it's NOT supported by the pwc or pwcx driver modules. I suspect it's support by the gspca_sn9c20x or gspca_sn9c2028 driver modules, but I'm still wrestling with them. More updates to come.
Edit/correction: out-of-the-box, and using the gspca_sn02028 driver, the microphone works fine (or at least, it shows moving bars in the Gnome sound preferences window). Video's non-existent via the Cheese application (gstreamer-based). I'll try using another application. Also, I've tried installing libwebcam0, which isn't installed by default, but still don't have success. /dev/video0 isn't showing up at all.
Further edit: According to this page (you'll want to run it through a translator, since it's in French):
This chipset/camera has been supported by the sn9c2028 driver--which may or may not have become the gspca_sn9c2028 driver--since August of 2008. I've downloaded that driver, but the only thing available on its Sourceforge project site is some very old "prototype" source code with a broken Makefile. I've not yet managed to compile it. Loading the gspca_2028 driver still gives me sound, but no video. I wonder if my camera is broken/defective. That would suck.
Another edit: looks like Sonics chipsets like this one are supported through the gspca series of drivers. Unfortunately, this particular device ID, 0471:0321, is NOT supported. It's purported to be the same or a similar chipset to other ones that are supported, so I'm wondering if it's possible to "trick" the driver into trying to make it work, anyway. That's really a long shot, so I doubt I'll get this working on Linux...which is sad. I guess I should finally break down and get a supported webcam. :-(