May I give you an advice? I would go for a firewire webcam and not usb. You will face some probs with usb webcams and will need to go for third party drivers which will cost you a little bit. You can pick any firewire webcam. Everything will work just fine. I have the D-Link 350C (or so) and I can use it perfectly with yahoo. My Aiptec USB webcam caused me a lot of pain and I needed ioxpert drivers (no freeware!) so yahoo could use the webcam.
Simply go for the cheapest firewire webcam you can find. No matter if the company says that it is just running on pc...
iBook 600; 12''; 640mb; 8mb Rage; DVD-CDRW-Combo, 20GB
P4 1.6; 2x80GB Raid1 (file-server)
tiBook 1Ghz, Superdrive, 768MB, 64mb 9000, 60GB