If you are using Mac OS X, you should have come across Growl. Growl is a notification system for Mac OS X, it allows applications that support Growl to send you notifications. Notifications are a way for your applications to provide you with new information, without you having to switch from the application you’re already in. I think this feature is really useful for our web applications as well. Daniel Mota has created Growl 2.0 with Mootools, so that we can easily integrate this effect into our web applications.

Growl 2.0 with Mootools

Requirements: MootoolsFramework
Demo: http://icebeat.bitacoras.com/mootools/growl/
License: License Free