Installing IRC Software

XChat (Windows, free & open source)

mIRC (Windows, shareware)

irssi (Linux/Unix, free & open source)

KVIrc (Linux/Unix, free & open source)

ircII (Linux/Unix, free & open source)

Ircle (Mac OS9, shareware)

PJirc (embedded in your website, free & open source)

Also, help installing your own IRC server (caution, advanced: for network administrators only)