DockStar is the smart way to keep an eye on your Mail. It allows you to add new badges to the Mail dock icon and clickable indicators to the menu bar. DockStar lets you keep track of email in various accounts and folders, RSS feeds, Notes, and To Do items with customizable badges in the Mail icon, menu bar, Dashboard, and even in a Screen Saver.
Mia for Gmail (was Notifier Pro for Gmail) is a desktop Gmail client which sits politely in your menu bar.
