Yahoo Messenger for iPhone [iTunes link], which debuted in the app store this morning, does more than just let you chat with your buddies. The application's feature set offers the next best thing to online IM, and it's all packaged inside a slick and easy to use interface.
Yahoo Messenger is free to download, and instantly lets you plug into your Yahoo network for instant messaging on the go. Not only can use the app to chat, but you can add buddies, update your status (with links), add emoticons, and even exchange photos.
A few cool additional things you can do include the ability to sign in or update your status as invisible - we all have one reason or another to use that feature - or remain logged in an idle state when you're playing with other apps or talking on the phone. The idle setting means that you can continue to receive messages while away, and view them when you return to the app.
Yahoo Messenger's pocket-friendly app is one of the neatest mobile IM apps out there and it's also available for Blackberry and Sidekick via the Yahoo! Mobile product site.
For more info on the app, read Yahoo's blog post on the app, or watch this short video:
More iPhone Resources From Mashable