As well as being the alias of Tricia McMillan, a character from Douglas Adams' The Hitch Hiker's Guide to the Galaxy series, Trillian is a win32-based instant messenger client.

With support for all the biggies -- IRC, MSN Messenger, AOL Instant Messenger, ICQ and Yahoo! Messenger -- Trillian attacks the problem of different groups of friends choosing different instant messenging mediums head-on. A recently-integrated plug-in architecture will make it much easier to implement support for other chat networks in the future (Jabber, for example).

Developed by Cerulean Studios (Kevin Kurtz and Scott Werndorfer, art by Ryan Saghir), the first public release of Trillian (supporting only IRC) appeared July 1, 2000 -- AIM, ICQ and MSN support was added November 29, 2000 and Yahoo! Messenger appeared December 23, 2000.

A few noteworthy features:

Best of all, some of the less persistent unpleasantness simply goes away when adopting a different client. Well, at least the advertisements and nags do.

Trillian is freeware and is under active development -- the usual problems plaguing some of the other 'unofficial' clients are quickly taken care of.

Early February of 2002, AOL declared war on all unauthorized third-party AIM clients -- Trillian's developers have released a number of patches in order to circumvent AOL's attempts to shut down the client.

In September of 2002, the Trillian developers released Trillian Pro v1.0, a flavour of Trillian with extended features, intended primarily for corporate use.

http://www.ceruleanstudios.com