After listening to the advice of the list on which webcam to get, and finding it surprisingly difficult to find a webcam that has a corresponding driver from the source forge repository - I've decided to hire an Apple i-sight from college for the weekend to see how I get on with it before committing to the £80 odd for a purchase!
It's working so far, except when I open the settings via the [dialog( message, PD (or perhaps rather the config panel) freezes, then shortly afterwards quits.
(OS X 10.4, PD-0.38.4-extended-RC7, GEM 0.90.0)