Pidgin is an instant messaging client which also supports IRC.
Smuxi is an irssi-inspired, flexible, cross-platform IRC client targeting the GNOME desktop.
Pidgin is an instant client which also supports IRC.
XChat is a graphical IRC Client with a GTK+ GUI. It has a look and feel similar to AmIRC for the Amiga. It includes the mIRC extension DCC RESUME and mIRC color, multiple server/channel windows, dialog windows, and a plugin API.
LostIRC is a simple IRC-client. It features tab-autocompletion, multiple server support, automatic joining of servers/channels and DCC sending which should cover the needs of most people. The client is 100% keyboard-controllable, and uses the gtkmm GUI library.
Quassel is a modern, cross-platform, distributed KDE4/QT4 IRC client.
Konversation is a client for the Internet Relay Chat (IRC) protocol. It is simple to use and well-suited for novice IRC users.
KvIRC is a command line/text based IRC client.
WeeChat is a command line/text based IRC client.
With any client you may want to obtain a cloak to hide your IP, and hostname from DoS attacks. An unaffiliated cloak may be obtained by asking a FreeNode staffer.