Adium X is a fast and lightweight, yet highly customizable, multiple protocol instant messaging application for Mac OS X. It uses libgaim, and is based on a plugin architecture. It features partial address book integration and a compact contact list.
buddhaIq is a Java instant messaging client library. It can run as a standalone app in console mode, send and receive type 1 text messages, detect status changes of a contact, and retrieve your buddylist from an ICQ server.
The RSS-IM Gateway allows you to let visitors
read your RSS feed through an instant messgaing
network such as AIM, MSN, ICQ, YIM, or Jabber.
It is very easy to set up and can easily handle
hundreds of users.