Below are several of the most popular of the many IRC clients currently available:
*Windows
**[http://www.silverex.info/news/ FreeX-Chat] Free compiled version of X-Chat for windowsWindows.
**[http://www.mirc.com mIRC] The king of windows IRC clients
*Linux
**[http://www.irssi.org/ Irssi], IRC client that runs in the console.
*Mac
**[http://xchataqua.sourceforge.net/ X-Chat Aqua], good IRC client based off of XChat X-Chat but lacks some features.
**[http://www.g1m0.se/macirssi/ MacIrssi], a good IRC client that doesn't have as many features as X-Chat Aqua. Basically a GUI for IRSSI.
** [http://colloquy.info/ Colloquy], a native Aqua IRC client that integrates well into OS X and offers a rich featureset.