Isn't it wonderful that Address Book has a function built right in that allows you to merge duplicate entries? This becomes particularly valuable if you use a contact synchronization tool such as Plaxo. It's so useful, you'd think that iCal would have something similar. As you know, if you've run into the problem of having multiple duplicate appointments polluting your iCal calendar, there's nothing built in that will help you out of your mess.
Luckily, John Maisey has created both Leopard and Tiger versions of an AppleScript that will sift through the calendar of your choice and kill off duplicate appointments. Don't be alarmed if it doesn't appear to be doing anything when you first run it. In our brief test, it took about 13 seconds to delete 15 duplicate entries, so this script is no speed demon. But what it lacks in terms of speed, it more than makes up in utility.
As with any script or utility that deletes data, be smart and back up your iCal data before you try it.