Purchasing a Webcam for Linux
If you don't already own a webcam, then it's important to note that not all webcams will work properly with Linux (-especially the cheaper ones, in my experience). The thing to look for, when buying a webcam for Linux, is if the device conforms to the UVC (USB Video Class) standard.
Some manufacturers (-such as Creative Labs) do go to the trouble of specifying if their webcams work under Linux, but many do not. I would recommend you check the box or literature for any mention of Linux or UVC if you are physically buying it in a shop or – if you're lucky - you may even find a sales assistant who knows what you are talking about!
If you are buying online – or researching prior to buying – I believe the following pages to be the best resources to give you a definitive answer on whether your desired webcam will work (-properly) under Linux: