Basically any _UVC - USB Video Class_ compliant webcam will work on OS X 10.4.3 (ideally 10.4.11) and up. It does require a USB 2.0 speed port. It's a rapidly emerging 'driverless webcam' standard that eventually all webcams will adhere to - not just the Mac but for ANY computer platform. Only Logitech's top end Pro models, or Creative Labs mid to higher-end cams for example are UVC compatible. Others in their mid to low end are NOT. Hercules & HP make some decent UVC cams as well. Check out
http://www.uvccompatiblewebcams.com/ for a wide range of options.
Recently, many cheap far-east import cams are beginning to flood the market, mostly via eBay. Most are just absolute junk even if they are UVC compatible. The lousy MacAlly IceCam2 is one of these: in my opinion, a $10 junk import cam rebranded and sold for $30. So beware the bottom of the barrel, ya want cheap, ya get cheap.