Google Notifier for Mac can no longer be downloaded. Take a look at the e-mail notifiers section.
Google Notifier is the perfect menu bar companion if you need access to your mail and calendars at all times. Thanks to the application, you can get notified of new messages, check your mail create new Google Calendar events in a few clicks. All you'll need to use the Notifier is a Google Account, and you'll have to enter your username and login the first time you launch the application.
Google Notifier can be customized so that you receive a pop up message every time a new message arrives in your inbox. You can also set a sound for new mail and for calendar reminders.
Google Calendar and Gmail both show up as separate in your menu bar, something which I personally do not like but that some of you might prefer to separate mail and events.