Yahoo! Messenger is a free service that allows you to see when your friends are online and ready to talk, send private, instant messages so no one else can hear, get instant alerts for new messages in your Yahoo! Mail account, and keep track of your stocks portfolios and use stock price limit alerts.

Features:

* Free PC-to-PC calls* -- regular phones for dirt cheap

* Personalize Messenger with fun plug-ins

* Listen to free Yahoo! Music LAUNCHcast radio

* Instant messaging

* Drag and drop photo and file sharing

* Share IMs from your mobile phone

* Share live video with your webcam

* Use fun Emoticons, Audibles, and Avatars

* Catch up on friend's lives with Yahoo! 360° built right in

Yahoo! also offers PC-PC, PC-Phone and phone-to-PC service, file transfers, webcam hosting, text messaging service, and chat rooms in various categories.

Other features include the ability to create a chat room automatically, stock price alerts, the ability to send messages to friends (even if they're not online when you are), a Quick Compact mode that hides the Messenger tools to maximize your viewing area, Messenger Themes, and voice chat, which allows you to talk for free to anybody else on the Internet. It also includes Launchcast Radio, Yahoo Games, and Yahoo Audibles. Using a Webcam, you can see who you're chatting with or view the Webcam of any Yahoo member who has granted you access.

Yahoo! has announced a partnership with Microsoft to join their instant messaging networks. This would make Yahoo! Messenger compatible with Microsoft's .NET Messenger Service. It also made Microsoft's Windows Live Messenger compatible with Yahoo!'s Network. This change has taken effect as of 2006-07-13, - Yahoo! Messenger has integrated instant messaging with Windows Live Messenger users, and is fully functional.
Yahoo! Messenger was originally launched under the name Yahoo! Pager on 1998-03-09.

Entertainment

• Photo Sharing. Drag-and-drop photos into your IM windows and talk about them like you're there.

• LAUNCHcast Radio. Make your own radio station and listen to music you like!

• Yahoo! Games. Right in your IM window, challenge friends to a Game of backgammon or pool while you catch up.

• IMVironments. Use interactive themed backgrounds in your IMs.

Productivity

• IM Windows Live™ Messenger friends - New! Share IMs (and more), plus see them on your Messenger List.

• Yahoo! Calendar. Stay organized and get calendar alerts.

• Contact Search Bar. Quickly find a contact to IM, call, SMS and more.

• Find, Add, Share Friends. Easily get connected with the people who matter most.

• Yahoo! Search. Find what you need right from your IM window.

• File Transfer. Share files with friends instantly.

• Address Book. Synchronize all your contact information.

• Stealth Settings. Make yourself appear online to some and offline to others.

Personalization
• Plug-ins - New! Add content, services and games to Messenger.

• Sound effects - New! Play fun sounds or a song during PC calls.

• Audibles. Let these animated characters say it out loud for you!

• Emoticons. Express your feelings with these animated smiling faces.

• Yahoo! Avatars. Represent yourself with a stylized graphical image.

• Display Images. Select an image to represent yourself to your friends.

• Skins. Select new visual designs or disable them altogether.

Communication

• Chat Rooms. Join a live, group chat room to discuss a variety of topics.

• Make Calls From Your PC. Make free worldwide PC-to-PC calls, plus free voice mail.

• PC-to-Phone Calls* - New! Call regular and mobile phones for as low as 1¢/min.

• Phone-to-PC Calls* - New! Get a phone number for your PC so friends can call you.

• Connect on Yahoo! 360° - New! Stay up to date with friends' blogs, photos, and more.

• Take Yahoo! with You. Send and receive IMs on your mobile phone.

• Webcam. Share live video with friends and family around the world.

• Conference. Exchange text messages with multiple people in one IM.

NEW in Yahoo! Messenger 10.0.0.542 Beta:

Improvements in the webcam detection logic:

- If you were able to use your webcam on 9.0 or other IM programs, but not on Yahoo! Messenger 10, this fix should take care of the issue.
Explanation for grayed-out video call button:

- If your video call button is grayed-out when you're IM'ing with a friend, it's because they're on an older version of Yahoo! Messenger. In order to receive your video call, they also need to upgrade to Yahoo! Messenger 10 Beta. To help reduce confusion about this, we added an inline message explaining this.

Smoother handling of unanswered calls:
- When you make a call to a friend but they don't answer within 20 seconds, the call is automatically terminated. Previously there was no messaging about this, so we added one to let you know that your friend did not answer your call.

Better explanation for downgraded video calls:

- In the event your internet connection can no longer support the full video call (e.g. video + voice), the conversation gets downgraded to a voice-only call. When this happens, the video picture disappears. This is the correct behavior, but we added some inline messaging so you'll know when and why it's happening.