Mail2iCal for Mac

From KleinWare:

This script will convert messages from Mail.app into iCal events or todo items. Place the script inside the folder ~/Library/Scripts.

There are two methods to use this script:

1. Manually The installer will add the AppleScriptMenu to your menubar, if you want to. Select the messages you wish to convert and call the script by selecting it in the menu
2. Automatically from a mail rule. The installer will create some example rules for you.The target calendar will be determined from the rule name. The script will automatically be called on all messages that your new rule applies to

To change the target calendar, run the script with no messages selected in Mail. You will be prompted with the option to reset. If you click 'Reset', you may choose an existing calendar or create a new one to contain your messages.