If you want your customers can contact your support dept via Skype/YahooIM from your site, you'll create the link to launch Yahoo or Skype. Just like these images:

Your visitors will automatically lauch their Yahoo/Skype when they click to above image

You can switch displaying image: big, medium, small or tiny...

Download: http://www.onboom.com/downloads/mod_onboom-chatme.zip

Good luck!
Enjoy it