FireIRC is an IRC Client that brings the ideas of mIRC, X-Chat, and Linkinus all into one client. With FireIRC you get lots of extendability for whatever needs you need on IRC.
My Socialent is a web based multimedia utility with a social network at it's core that has hard coded API's for native websites/networks. My Socialent is currently is planing/development stages.
fMessenger is an IRC client written in the Java programming language using the SWT toolkit. It is extensible using Java classes or Groovy scripts. It complies to the RFC 2812 and 1459, cause it is based on the excellent IRClib from the moepII project.