When you're working on your Mac, sometimes things happen in the background that you would like to keep track of while working in another application. Growl works with hundreds of popular Mac apps to notify you of specific tasks like when a download is complete or when your CD-burning project is finished.
For example, it will tell you in Adium when a friend comes online while you're working on something entirely different, and it can notify you when your EOD backup is done.
We like having control over what gets a Growl notification, and the ability to choose from numerous skins to customize the look of each notification. Overall, if you're looking for a way to always know what's going on with your running applications, this free program is an excellent way to stay notified.