JawTek's latest project Web2Notify has been released. Web2Notify is designed to bridge the gap between the web and your notify client (i.e. Growl™, Snarl™, Mumbles™).
Web2Notify can be found at: http://sourceforge.net/projects/web2notify/
And userscripts that add Web2Notify functionality can be found at: http://userscripts.org/tags/Web2Notify