Two months ago, Hawk Wings posted about an iCal hack for using Growl to display its alerts. It was clever, complicated and sacrificed the ability to email alerts.
Thomas Aylott has improved on the hack 
, writing a smarter script that enables Growl notifications by default, but which preserves the ability to email alerts as normal.
It is still complicated and involves digging around in the iCal package, replacing scripts. If you like that kind of thing and you like Growl, you will want to try it out for yourself.
This will definitely come in handy. Thanks for the heads-up!
I recently updated the script and put it in a nice disk image with instructions and symlinks to everything. It’s way simple now.
applescript hack that makes Growl work with iCal properly
Growl iCal Alarms.dmg
Thanks, Thomas. I’ve given the disk image a post all of its own.