A simple to use Firefox extension that can notify you when you have new mail.

Yahoo! Mail Notifier is a small extension that is meant to notify you when new messages arrive in your Yahoo mailbox.

Notification options include: customizable sound, notification alert, status bar and toolbar icon. Also allows the user to map different mouse buttons to open Yahoo Mail in different tabs,windows,etc.

 Download: Yahoo! Mail Notifier 1.0.0.12