The Logitech brand name is king when it comes to the webcam market, and their product line-up is unmatched. For general use, the baseline HD Webcam C310 offers a ton of features such as a 5-megapixel camera plus standard features such as 720p HD video, a built-in microphone and face tracking. It is designed to conveniently clip to the back of a flatscreen monitor, so it is a perfect fit for a desktop or laptop. In addition, Logitech put a five-foot long chord on it so you can mount it anywhere you like. It is currently selling on Amazon.com for less than $40.
Logitech's next up model is the HD Webcam C510 which as an 8-megapixel camera and a 360-degree rotating camera, which gives you more options for placement compared with the previously mentioned C310 model, which is fixed. It currently sells for $43 on Amazon.com.
The real high-end Logitech stuff includes models such as the Webcam C905 and Webcam Pro 9000, which both feature glass Carl Zeiss brand lenses, as opposed to the cheaper plastic lens you will find on the lower-end models. These two models sell for around $50-60 and offer the same features inside a different housing. With the superior lens and better autofocus capabilities, these cameras might be worth spending a few extra dollars.
If professional-grade optics is what you need, then you can go with the QuickCam Orbit AF with its motorized pan and tilt camera. It retails for about $90 and has a Carl Zeiss lens, 8-MP camera, 720p HD video and autofocus. It is the most expensive model Logitech makes. For a higher quality picture, you may also consider the HD Pro Webcam C910, which has all the same features but also comes with a 10-megapixel camera and dual microphones for stereo sound input.