I switched my main machine from Fedora and Gnome to Mac OSX and missed having the Zapplet. I wrote a little script to scrape a Zenoss Event View and pipe to growlnotify.
The source is on github here
It was written quickly so may need some massaging to work on your system. If you have trouble, email me seth AT migrantgeek DOT com.
SHA1 sum for zenoss-growl-notify.tgz