Digsby has a great little widget to allow you to have live chat on your site. Please look below in the right side and I have added this widget to the blog. This allows you to use your existing IM system (I use Digsby) to be a communication tool to your web visitors. You could use this for support or sales.
Here is the url: http://widget.digsby.com/
I use Digsby for my IM client. It allows me to consolidate the multiple IM systems I use (MSN, Gtalk, AIM, and yahoo)