Growly Calendar is a straightforward scheduling tool designed for everyday home use. It works great if you have just one computer, but it really shines when you want to coordinate calendars across multiple computers. You don't need a server, a MobileMe iDisk, or any other kind of central access point. All you need is an email account on each computer that you want to synchronize.
This is not a business calendar: you specify starting times for appointments but not their length. It doesn't have fancy doodads for handling overlapping events. It can't coordinate different peoples' schedules. What it does very well is keep track of appointments in your family's day, as well as holidays, birthdays, and other special occasions.