Use a Digsby widget in your sidebar, on a page or post or by a link to use a pop up with the Digsby widget inside.
Digsby is a multiprotocol IM client that lets you chat with all your friends on AIM, MSN, Yahoo, ICQ, Google Talk, and Jabber with one simple to manage buddy list. Digsby also includes options to check email and stay in touch with your favorite social networks like Myspace and Facebook.
With WordPress Digsby you can place a widget on your WordPress site so you can chat with visitors right from Digsby. Digsby is required to be installed on your local computer for you to be able to chat with users on you website.