When you create a new event if you click "Alarm," you get several choices, one of which is "Open File." Yup, this can open anything you want including, of course, AppleScripts. Simply select the script you want to run, choose the time of day and interval, and you're off! Plus these will run even if iCal is closed, just like any other alarm message.
Combined with the new (born again!) scheduling feature in Panther's Energy Saver panel, this makes for a quick and easy method for running maintenance jobs (or anything else you want) before your first coffee in the morning.

