XChat is a free and powerful IRC chat program, especially popular for Linux. XChat 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.
X-Chat Azure is Mac OS X native front-end for XChat that will allow one to experience its amazing features using a Mac native user interface.
X-Chat Azure comes with built-in support for 41+ locales and xchat 2.8 core features.