(Credit: CNET Networks)

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, such as when a friend comes online in your chat client, you receive a new email or Skype call, or your CD is finished burning.

Fortunately, there's a free notification system called Growl that has become a Mac favourite for its flexibility and elegant interface.

Several applications are already Growl enabled. (Credit: CNET Networks)

You can configure Growl to notify you when a download is complete, when a DVD is finished ripping, when your FTP client is done uploading or downloading, or have it send you an email at work when your Mac at home is finished backing itself up.

Growl was designed to let software programmers easily tie into it, letting them build custom Growl notifications into their programs, so the instant you enable Growl, every Growl-enabled application on your Mac will immediately offer a whole new realm of features. The list of Growl-enabled applications contains more than 100 well-known programs, with the list growing all the time.

Choose from several different Growl notification styles. (Credit: CNET Networks)

Along with the added control of knowing when things are happening behind the scenes, you have complete control over what Growl shows you. A comprehensive display preference panel lets you customise the programs that work with Growl. This way you'll never receive notifications you don't want. Simply use the Growl preference pane to turn off any or all notifications. Growl offers a huge list of styles so your notifications can fit your overall desktop theme or display certain styles depending on the program. It's your call, and Growl is easy to configure.

Growl already works with several popular Mac applications (listed here) and more are on the way all the time. If you've been looking for a way to be notified when specific things happen behind the scenes on your Mac, Growl is the perfect application for the job.