Most of our code is written in Java here at Bizo. This means we heavily rely on Ant for building, testing and packaging our applications.
Sometimes I found myself watching the scrolling terminal waiting for a build to complete. Other times, I left the terminal to go off and do some other task while the build was happening, only to realize some minutes later that my build was probably done. What I wanted was a way for Ant to notify me when the build was complete so I didn't have to stare at a terminal or forget about the build. What I wanted was Growl notifications from Ant!
If you don't know what Growl is you can read about it here. Its basically a notification API for Mac OSX and very widely supported and used (other applications that use it include Adium and Quicksilver for example). (BTW - All Bizo developers get Macs...)
Doing a little searching turned up this blog post. It was pretty easy to get this task integrated with our build system... And now, growl tells me when my build is done!