Growl for Mac sends you notifications about the tasks running in the background, shows you previews of incoming emails in real time, and can even tell you when one of your chat buddies comes online. It basically enables you to keep track of what's going on in the background while working in another app.
Notifications for system events: With Growl for Mac you can choose what apps to receive notifications for through downloadable and configurable plug-ins. Because it integrates with most popular Mac apps, you can receive all kinds of useful notifications, for new emails, new social messages, or the completion of a scheduled process or task.
Wide range of supported apps: It supports many common programs that as a regular Mac user you are likely to use, including Adium, Yahoo Messenger, Twitter, Monitor for Facebook, as well as a wide range of utilities, games, music, and entertainment apps.
Email previews: The snippets of new emails it shows you can help you decide whether the email is worth your attention or not.
Doesn't work with certain native Mac apps: In our tests, Growl didn't seem to work with Safari or iTunes.
Not for light users: If you use only one application at a time and don't run many programs in the background, you don't really need it.
No free download: The lack of a Lite version or at least of a trial version strikes us as odd. If you want to use this app, you have to buy it.
If you have a lot of running programs to monitor, Growl for Mac can make your life a little easier, saving you the trouble of having to switch between apps all the time. Because there's no trial version available, however, do check the developer's website to make sure it supports your favorite apps, or else you may be wasting your money on it.