Become a MacRumors Supporter for $50/year with no ads, ability to filter front page stories, and private forums.
the iSight camera has a good design which will match your Mac Pro but its too bulky and expensive even though its discontinued. you can get one on eBay.

the Logitech QuickCam Vision Pro far exceeds the image quality of the iSight and has a smaller profile. is made for Mac and is cheaper. it also has a light.
 
I like the Logitech cameras. I have a Logitech Quickcam 9000 that works really well.
 
Register on MacRumors! This sidebar will go away, and you'll see fewer ads.