Few days ago, a new version of AMSN (0.98.1 stable) was released. AMSN is a Microsoft Messenger clone. It allows you to keep in touch with your friends and exchange instant messages and files. This version makes aMSN a complete msn clone for Linux.
aMSN main features include: Offline Messaging, Voice Clips, Display pictures, Custom emoticons, Multi-language support (around 40 languages currently supported), Webcam support, Sign in to more than one account at once, Full-speed File transfers, Group support, Normal, and animated emoticons with sounds, Chat logs, Timestamping, Event alarms, Conferencing support, Tabbed chat windows.
More features can be added to aMSN with plugins , or completely change its look with different skins
For ubuntu :
sudo apt-get install amsn
For Mandriva :
For Fedora :
yum install amsn
For other distros see this page