Yahoo Messenger is a free service that allows you to see when friends come online and to send them instant messages.
Connect with all your friends:
Instant message friends on Yahoo! and Windows Live™ Messenger. See which friends also use Yahoo! Messenger
Stay in control…24/7:
Decide who sees you online with stealth settings
Share away:
Swap photos and monster files (up to 2GB) in real-time. Plus enjoy voice calls and webcam video
Mirror
http://rd.software.yahoo.com/msgr/9/msgr9us.exe