Mail Unread Menu
Mail Unread Menu is a simple menu bar application which can provide you with a quick and easy way to see how many unread email messages are in apple's mail. unlike other menu bar notification applications, mail unread menu is actually a plugin for mail.app, which means that the count is instantaneously updated whenever you receive new email or change the status of a message.
ManilaMail is an itty bitty ?status bar? application that controls some of the most vital functions of Apple Mail in Mac OS X. This application is based off of the Gmail part of the Google Notifier and as such it is extremely light weight.