You gotta look into these two Open Source projects if you are into Instant Messaging, or need to set up an Enterprise-wide IM Server where you work!
“Wildfire is a leading Open Source, cross-platform IM server based on the XMPP (Jabber) protocol. It has great performance, is easy to setup and use, and delivers an innovative feature set. Wildfire is an enterprise instant messaging (EIM) server dual-licensed under the Open Source GPL and commercially. It uses the leading open protocol for instant messaging, XMPP (also called Jabber). Wildfire is incredibly easy to setup and administer, but offers rock-solid security and performance. Use Wildfire in your organization as a more secure and feature-rich alternative to the consumer IM networks. Or, replace your existing EIM server with a more open, easier to use, and much less expensive solution.
Spark is an Open Source cross-platform IM client optimized for businesses and organizations. It has a simple but powerful user interface, leading feature set, and uses the open XMPP (Jabber) protocol. Spark is an Open Source, cross-platform IM client optimized for businesses and organizations of all sizes. It includes enterprise-class features such as built-in support for group chat, telephony integration, and strong security. It also offers an exceptional experience with user-friendly features like in-line spell checking, group chat room bookmarks, and tabbed conversations. The plugin architecture allows you to build plugins (Sparkplugs) that quickly and easily add new features tailored to your specific business needs. Spark is centrally managed from within the Wildfire administration console, making it easy to provision, update and manage all clients on your network.”