MSN Messenger (now Windows Live™ Messenger) is a “chat” program allowing users who have a Microsoft® .NET Passport or Yahoo! account to chat to other users who use compatible chat programs. Freely available from MSN, or chat instantly online at webmessenger.msn.com.
I currently use MSN Messenger© in addition to mIRC. It allows for voice chat and a few other advanced features not implemented in IRC, although worse in most other ways. Contact me if you think you deserve to be added to my authorised users list.