Video chatting is great, but a bit grainy. If you’re using Skype, you can improve the quality of the video by following this tutorial on Skype’s dev zone
Open your Application Support folder (in your personal library) and navigate down to Skype. Open the folder inside with your skype user name. Open the config.xml file and add the following two attributes inside the <video> tags: <CaptureWidth>640</CaptureWidth> and <CaptureHeight>480</CaptureHeight>. Save your changes, launch Skype and place your video call. The receiving party should receive video at 640×480 resolution rather than the standard 320×240.
Jason Ball 
any idea for the windows users ?
Sorry, can’t help you there…