aMSN is a free open source MSN Messenger clone, with features such as:

• 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

For a full list, see the features page. More features can be added to aMSN with plugins, or completely change its look with different skins.