We bought one very similar to this a few years ago and it is brilliant. Easy to use and not badly priced.
Your best bet may be going into somewhere like PC World so that they can show you how to use them. Luckily dp is good with computers so set it up easily but my cousin has had problems with hers. Logitech seem a good brand though.
They are definitely worth it as relatives who live far away can see your lo x
Don't know in detail specifics on brand, but from what i found when I was looking at webcams then you should get something pretty good. It is possible to buy them for about £6, but I guess the quality won't be great. You need to decide what image quality you want and whether it needs to have a built in microphone etc. But afaik, will all be wasted if who you are talking to as a cheap crappy thing.