Quassel IRC is a modern, cross-platform, distributed IRC client, meaning that one or more clients can attach to and detach from a central core, much like the popular combination of screen and a text-based IRC client, but graphical. In addition to this unique feature, it aims to be a comfortable chatting program.
CodingTeam is a software forge that is lightweight and extensible. It provides a lot of collaborative tools. With this software forge, projects can benefit from basic features (such as screenshots, downloads, uploads, and news), communication features (such as chatrooms, forums, the OpenForge API, and Jabber/XMPP integration), and development features (such as a VCS code browser, a bug tracker, SVG statistics, timeline, and roadmap). Also provided are community tools (project browsing, tag clouds, notepad, and user profiles).
JTelIRC is an advanced IRC framework for Java. It is mainly intended for writing automated clients ("bots"), but may be used for normal clients as well. It provides an intuitive and well documented Java interface to IRC and makes it extremely easy to write advanced clients quickly.
Bip is an IRC proxy that supports replaying logged conversation and multiple clients on one IRC server connection. It has a handy logging directory structure. It is multi-user and has a flexible configuration. Some of its configuration can be changed at runtime with special IRC commands.