Speed/refresh - You may see this listed as pictures-per-second. Some of the cheaper cameras may only handle 8 to 10 pictures per second (PPS) where as the new professional cameras manage up to 120pps. Your computer's capabilities and the camera’s software could also have a negative impact on number of pictures per second.
Resolution - Measured as expected - in pixels for digital video. Standard-definition television is specified as 720/704/640×480i60. New high-definition televisions (HDTV), are capable of resolutions up to 1920×1080p60, i.e. 1920 pixels per scan line by 1080 scan lines. 2.0 megapixel, 960 x 720, is the new current standard (April 2009).
Lighting - Newer lighting technology and enhanced optics make low-light viewing less of a concern. If you will be often using your camera in areas with low available light, consider putting some extra dollars into the higher-end optics such as Carl Zeiss lenses. Cameras for capturing outside pictures will need to be either placed under an awning or eave, or have an extended or moveable lens cover.
Focus - Most web cameras have permanent, fixed focus. Higher end models have manual and/or auto-focus. If you are purchasing a web cam to view your property, fixed will work as will manual for adjusting the camera to your preferred view, length, or distance.

Sony MHS-PM1 Webbie HD Camera, Silver
The online world and it's web sites are moving more and more towards video clips - are you ready?
This will help...
Use this pocket sized, cell phone-style camera to capture life's priceless moments.
Take 5mp still images, record 1080p HD video; built-in LCD screen, 270° rotating lens, and 4x digital zoom. Available in several colors - like orange and yes, eggplant...
Sony MHS-PM1 Webbie HD Camera, Silver
Sound - The majority of mid-range or better web camera have built in sound capability. Quality is based on, as usual, dollars invested. Newer models work with Skype which can include free full-screen video calling.
Mobile or stationary? - Will you use your camera at home attached to your PC or will it need to travel? If you’re a traveler, you’ll want a camera with a recessed lens or you might want to invest in a pouch-type bag for carrying your camera.
TIP: If you have a flat-panel LCD, make sure the camera you purchase can be clipped to a flat panel screen – some models can not. Otherwise, a ball-type web cam can simply sit on top of the monitor.
Connectivity - Webcams may use USB and Parallel or Serial ports. USB 2.0 has transfer speed up to 30 fps, which can produce the best image quality as it’s the fastest interface available. USB 2.0 compatible may mean the camera will work, but not use the full range of USB 2.0 functionality.
Video effects - Need to morph yourself or create an avatar? Plan on spending over $50 for your web cam and have some fun.