I look into this a couple of weeks ago...
The Logitech QuickCam Vision Pro for Mac seems to be the webcam to get for OS X!
Here is a site which seems to have a current review of Mac webcams and they recommend it:
The Logitech QuickCam Vision Pro for Mac is at NewEgg:
But cheaper at Amazon.com now:
I have my new Logitech QuickCam Vision Pro for Mac here in a box waiting to install... I guess it is time to install it!
EDIT: I just spent a few minutes playing with this webcam on a Intel BadAxe1 Hackintosh with a vanilla 10.5.4 installation. It seems pretty decent and very easy to use. No microphone problems here. No drivers to install either, it just uses whatever is built in to OS X apparently. As far as mechanics go, I was expecting a more clip-like attachment to my monitor, instead the webcam sort of just lays on it (no big deal). I recorded some movies to test it out, PhotoBoth and QuickTime Pro (serial required) both work out of the box with this webcam as does iChatAV and other popular IM clients.
The camera is supposed to capture up to 720p (1280 x 720), but QuickTime Pro seems to produce a "native" resolution of 1600 x 1200. The frame rate seems to be pretty slow at this resolution. Fast motion is blurry. I suppose this is normal for webcams and acceptable for $100 video camera, but it certainly is a serious limitation for use. Switching to 640 x 480 (which QuickTime Pro compresses with H.264) solves most of that problem.