Google Hangouts
Also known as Google Talk, Google Hangouts enables you to run a chat service within your Google Apps domain. The chat can be text or video based. Thus, you can send instant messages or start video calls with other Google Apps users. When used in conjunction with Google Groups, Google Hangouts enables you to form teams, improve communication, and enhance teamwork online.
To find out how easy Google Apps makes it to set up your own chat service, follow this link to the Google Hangouts tutorial.
If you have not yet learned how to get your Google Apps domain, follow this link to the Google Apps Overview.