A Firefox add-on that adds a little status-bar icon that notifies you when you get a new message
Version: 0.1.6YMail Notifier adds a little status-bar icon that notifies you when you get new Yahoo! Mail. Click on it to change the frequency of checking and other settings.
Operating System: Mac OS X
When new mail arrives you can choose to be notified with sound, a sliding alert, or by running an external application. When there is no mail, the status-bar icon hides itself (optional) to avoid cluttering the screen.