This is called jQuery UI Notify Widget, that is similar to the Growl-like scripts we mentioned in the past, except most seem to come with an enormous footprint: 10-12k of code, X-number of images, and roughly 1000 options to support every plausible use case.
jQuery UI Notify Widget is built off the jQuery UI widget factory in approx. 100 lines of code and 100% CSS. In typical widget fashion, this implementation supports the most basic uses, but is flexible enough for more advanced cases.
Requirements: jQuery Framework
License: MIT, GPL License