To connect to an IRC server, you will need a program called a client. There are many IRC clients available to you and which one you use depends on what operating system you run and which client you prefer. The following is a list of the most popular clients out there for UNIX, Windows, and OS/2. Try them and decide for yourself which one is best.
ircii
ircii has been around almost as long as IRC itself. Although it lacks the color support of more recent clients many people still prefer it.
EPIC
Based on ircii, EPIC still retains much of the look and feel of ircii. A plus is the support for ANSI color which makes for a more aesthetically pleasing client.
Irssi
Irssi is a terminal based IRC client for UNIX systems. It also supports SILC and ICB protocols via plugins.
Xchat
"XChat is an IRC chat program for both Linux and Windows. It allows you to join multiple IRC channels (chat rooms) at the same time, talk publicly, private one-on-one conversations etc. Even file transfers are possible."
BitchX
Just as EPIC was based on ircii, BitchX was based on EPIC. It has its pros and cons so decide for yourself.
Zircon
Zircon is a client written in tcl/tk for the X windows system. If you prefer a more GUI driven client then Zircon isn't a bad choice.
mIRC
Quite possibly the most popular Windows client around, mIRC is a nice client for both the experienced IRC user and those who are new to it.
BitchX
Like the UNIX version above, but with a PM UI