Instant messaging over Google Talk or Yahoo can really speed things up at work, but you don’t want your employees wasting time online or being distracted by personal messages. You can replace access to those programs with the simple, free IP Messenger. Designed to work over an office network rather than the Internet, IP Messenger will keep everyone in your organization in touch.
Users can be sorted by the departments they work in. In addition, it is possible to see whether someone is at his or her desk. The interface is a little crude, but everything you need is there, including broadcasts to multiple users, sending messages to a specially created group , file transfers, and receipt notifications.
And the best part is that IP messenger is available for Windows, Linux and Mac OS, and is completely interoperable on all of these platforms!