HexChat - HexChat is a fork of XChat with bug fixes and new features.
WeeChat - WeeChat is a fast, light and extensible chat client.
irssi - Irssi is a terminal based IRC client for UNIX systems.
Kiwi IRC - A hand-crafted IRC client that you can enjoy. Designed to be used easily and freely.
KVIrc - KVIrc is a free portable IRC client based on the excellent Qt GUI toolkit.
The Lounge - The Lounge is a web IRC client that you host on your own server.