Skype - High quality video calls
To enable high-quality video calls with Skype for Mac, first download the latest version of Skype for Mac. You need version 2.5.0.85 or newer.
Then, quit Skype, navigate to /Library/Application Support/Skype/yourskypename/
I simply typed my username into Spotlight.
Find the file called config.xml. Open the file and find the
<Video>
<Device>Built-in iSight</Device>
</Video>
Add the following above that piece of code, but still within the video tags.
<CaptureWidth>640</CaptureWidth>
<CaptureHeight>480</CaptureHeight>
Save and close config.xml, restart Skype and do a video call. The remote party should now see your picture in 640×480 resolution, instead of the standard quality 320×240.