Miranda Instant Messenger: "Miranda IM is a multi protocol instant messenger client.No bloat, it's Easy and Small! Miranda IM is designed to be resource efficient and easy to use. It uses very little memory and requires no installation. Just unzip and run! This also makes it ideal for users that want to run their messenger client from a removable storage such as an USB memory stick. It can even be stored on a floppy disc if not too many plugins are used.
It's all about plugins!The powerful plugin system makes Miranda IM extremely flexible. Only the most basic features are built in, but there are currently more than 200 plugins available for download that allows users to extend the functionality in Miranda IM. Plugins can be installed to add support for ICQ, AIM, MSN, Jabber, Yahoo, Gadu-Gadu, Tlen, Netsend and other protocols.
Miranda IM is published under the GPL license and is free of charge.
Miranda IM supports Windows NT4, 95, 98, Me, 2000, XP & 2003."
I have just moved from JAJC to Miranda. Smaller and faster!