Miranda Instant Messenger is a minimalistic, free open source (GNU GPL) multiprotocol instant messaging application for Microsoft Windows.
Miranda provides a basic client framework and an advanced plugin architecture. Support for various IM protocols and additional features is implemented through optional plugins, some of which come bundled with Miranda by default while the rest can be downloaded from the Miranda IM website. This keeps Miranda lean and fast, since unused protocols can be removed. There are currently over 500 plugins for Miranda.

Miranda IM Features

• Customized look and function according to each individual's needs.
• Management and organization of hundreds of IM buddies on many IM networks
• Full message archive database
• Contact details or photos visible with mouseover
• No advertising or spyware
• Compact and portable: with few plugins, fits on a 1.44 MB floppy disk or USB flash drive with several plugins and even a large database.

Updates : Miranda Updates