Messenger is a free messaging service that allows you to communicate instantly with friends, family, colleagues and others.
Talk with your friends using instant messages, and even find out when they are online. The Messenger alerts you instantly when you have new mail in your Yahoo! Mail and Yahoo! Personals accounts, or when it's time for one of your Yahoo! Calendar appointments.
It even includes built-in Stocks, News and Scoreboard tabs so that you can keep track of all your personalized information, no matter where you're surfing on the Internet.