Miranda IM is a multi protocol instant messenger client for Windows. Miranda IM uses very little memory and is extremely fast. It requires no installation and can be fitted on a single floppy disc. Its powerful plugin system makes Miranda IM very flexible. Only the most basic features are built in, but there are currently more than 350 free plugins available for download that allows users to extend the functionality of Miranda IM.

Useful Links 

Miranda Home Page

Miranda Documentation

Miranda Addons

Miranda Download Page