This is the one I use...there are cheaper ones but I am really impressed with the quality of picture it delivers. Microphone works well, clear and loud sound. Looks good in all types of lighting also. I just plugged it in and it worked with everything, Yahoo messenger, Skype and still pictures. Great web cam, had it for about 2 years and works like new still.
http://www.newegg.com/Product/Produc...82E16826104088