I use my macbook with an Apple 23 inch monitor at work and so I can’t use the inbuilt iSight camera. Since Apple stopped selling the external iSight camera there is not much choice for Apple compatible web cams since most of the web cameras on the market don’t come with Mac OS X drivers.
One surprisingly option is the xbox360 web cam. This external usb camera works without any drivers and just plugs straight in and works. I managed to pick up a brand new one on eBay for A$35. The quality is pretty good and it sits without any problems on top of my monitor. Nice work microsoft.