The official Yahoo! Messenger app for mobile phones allows you to exchange instant messages with your Yahoo! or Facebookcontacts.
Once you've requested the download link and installed Yahoo! Messenger on your mobile you can start using the app to chat with your buddies by signing in with your account details. The application automatically imports all of your contacts, and groups them by whether they are online or offline.
To start chatting with the Yahoo! Messenger app, just tap on a contact, press 'r' or '7' to start typing your message. You can call up a history of your conversations by clicking on the 'Load previous' button. Besides sending instant messages, you can send a file to your contact from your phone, or even send them an SMS.
Yahoo! Messenger contains lots of options and settings, though you have to fight through menu screens to find them all, since most are contextual (meaning they only appear from certain parts of the app). Once you start using the Yahoo! Messenger app and learn the shortcut keys you'll find things much easier.
Among the options within Yahoo! Messenger are the ability to add contacts, update your status, change the way contacts are sorted and search contacts. You can import all your Facebook contacts into the Yahoo! Messenger app by signing in with your Facebook account details.
Although it's navigation isn't as slick as the iOS or Android versions, Yahoo! Messenger for Java phones still makes for a more fun alternative to SMS.