Webcams that have video quality of 720p or 1080p are normally the best ones to purchase.
The Logitech HD Pro C920 webcam 1080p is very nice. My friend owns this one and the Video and Picture quality is great. Also it comes with some useful software.
I own the Microsoft LifeCam Cinema 720p webcam I got a few years back. It is only 720p quality vs the above 1080p quality but 720p is still high quality enough for make nice videos and take pictures.
One thing to check is the microphone in the webcam. Some mics in webcams pick up a lot of the room noise. The only ways around this is pretty much using a separate microphone or having a quite room while making videos.