Eggdrop is an Internet Relay Chat (IRC) bot that can be extended using either C modules or Tool Command Language (TCL) scripts.

ircd-ratbox is an advanced, stable, fast ircd used on efnet and other networks.

centericq is an ncurses menu and window-driven IM interface that supports the ICQ2000, Yahoo!, AIM, IRC, MSN, Gadu-Gadu, and Jabber protocols.

BitlBee allows users to talk to people on the MSN, ICQ, Jabber, Yahoo!, and AIM networks with any IRC client by emulating an IRC server.