I have a Logitech webcam that works on XP and Vista, and I'm damn sure it'll work on W7 as well. Not because it uses
built-in drivers but because Logitech is a serious company that will likely continue supporting its products going forward. I'm not even sure Vista drivers won't work out-of-the-box in W7.
The last webcam I bought is a QuickCam Messenger (3 years ago) and is barely usable on Vista with hacked drivers where none of the webcam settings can be changed because the software doesn't recognize it. The official software has always sucked and installed
an unbelievable amount of background crap (updaters, notifiers, buttons support) causing huge boot slowdowns and wasting more than 50mb of ram even when not using the webcam.