If you need a slick client for your Gmail account –  up to four –  Notify is for you. It integrates itself into the menu and has more features than the simple google notifier.

“Since Notify sits up in your menu bar, it stays out of the way until you need it. When you do need, it, you can easily access all of your mail accounts in a manner that provides a much smoother user experience than traditional menubar notifiers.”