You can now create a Google Chat badge for your site where your site users can chat with you through Google Chat. A Google Talk chatback badge will let visitors to your web page chat with you. They’ll be able to chat with you whenever you’re signed in to Google Talk
http://www.google.com/talk/service/badge/New
You can also include chat in you Google Apps Sites.
http://www.google.com/talk/service/a/DomainName/badge/New