Yahoo recently released YM Beta 3 for download ( http://messenger.yahoo.com/mac.php )

<img src="http://img514.imageshack.us/img514/2100/picture3tl9.png" alt="Yahoo" />

-Yahoo! Messenger for Mac Beta
-Now with Voice!
-Instant message with Yahoo! and Windows Live™ Messenger* friends
-Have fun with emoticons, Avatars, and display images
-Share files, live webcam video, and more