I decided to put up this list which contains no less than 6 graphical IRC clients for Linux, powerful or user-friendly. I also provided several screenshots where I considered necessary and a brief description for each of them.
The GUI (Graphical User Interface) clients
XChat is built in GTK and it is one of the most powerful graphical clients for Linux, including scripting (Perl, Python, Tcl) and plugin interface, high configurability via the /set variables (like the conference mode, for example), support for connections to multiple networks (a must-have for any IRC client in my opinion) and much more. The forum and the #xchat @ Freenode channel are very helpful, and the documentation on the official site is abundant too. For GNOME users, a project called xchat-gnome is also available.
Being well-known for the fact that it's one of the most user-friendly clients for Linux, Konversation is also very popular among KDE users. It doesn't have event-based scripting yet, but it provides options for each and every need a user would need. Comes bundled with several default scripts like a media player announcer or a weather script to mention two of them. It integrates in the system tray, includes alerts and is very fast.
Another user-friendly client for KDE, KVirc provides a scripting interface similar to the one of mIRC for Windows, many configuration options, themes, support for multiple network connections, and much, much more. The only minus it has is that it's a little bloated and slow. Each new release is accompanied by a concept picture and codename, and documentation is abundant and included in the Help menu.
KVirc 3.2.4 'Anomalies'
In my opinion KSirc is the weakest client compared to Konversation or KVirc, but it comes by default with the KDE 3.5.x distribution, being included in the kdenetwork package. It supports scripting in Perl.
KSirc running in Kubuntu 8.04
Pidgin is formerly known as Gaim, the GNOME instant messaging client, also including a basic IRC client.
The official KDE IM client, Kopete includes a basic IRC client. Although they don't have powerful and fully-featured IRC clients, both Pidgin and Kopete can be used when you also use one or more IM protocols, like Yahoo! or MSN. This way, you can stay on IRC and IM using a single application.
Creating an IRC account in Kopete
Kopete 0.12.7 - #debian @ OFTC
Quassel is a basic KDE 4 IRC client which comes as default in Kubuntu. It does not support event-based scripting, but it offers several useful (and popular) configuration options.
Installation in Ubuntu
For every client, just use sudo apt-get install CLIENT_NAME with your user password. For example:
sudo apt-get install xchat
sudo apt-get install konversation
There are two versions for KVirc, 3.2.4 and 2.1.3. To install KVirc 3.2.4 use:
sudo apt-get install kvirc
And for 2.1.3:
sudo apt-get install kvirc2
Updated: March 29, 2009