Site Instant Messenger
Features: Completely stand-alone server; Configurable database schema - you may use any RDBMS system which has appropriate JDBC driver. From now you can use your own tables to make SIM server works! Just specify your custom tables for authentication and contact list; Low traffic usage; Has powerfull template-supporting engine. This is Java-applet which connects to the server at startup and allows you to chat with any user which currently on server.