For iCal, this depends on which version of Mac OS X you have.
For Leopard and later, the folder you need to trash is ~/Library/Application Support/iCal, where ~ is your home folder - the one with the house icon.
For Tiger and earlier, the folder is ~/Library/Calendars.
As for Address Book, it has a preference file called AddressBookMe.plist in ~/Library/Preferences, and a folder at ~/Library/Application Support/Address Book.