Data Detectors allow you to turn addresses, phone numbers and dates in mail messages into Address Book contacts and iCal events. You can also turn selected text into to-do items or stickies.
You can create tasks in Automator and then have iCal run them at a specific time in the future, or even as a recurring event. This example shows you how to have thumbnails of new photos automatically sent to an email address every week.
Snow Leopard includes a new version of iCal that lets you edit events in two new ways that make it much easier to use iCal as your calendar program. You can also easily import and sync Google and Yahoo calendars.
You can publish your own iCal calendar to MobileMe or to your own hosted server. Others can then subscribe to your calendar. It is a great way to make a list of events available to others.
Learn how to connect iCal to your Google Calendar. You can add events and update either one and they will synchronize within minutes.
Gary Rosenzweig shows you how you can subscribe to free and interesting calendars using iCal.