The Online Family answers:

There are a few ways to create a calendar that everyone in your family can use to note meetings, sport practices, school events, birthdays and more. First, does your computer already have a calendar program installed? Check your application file for iCal or Outlook, for instance. Or you can use a free web-based calendar so members of your family can access it from anywhere. For example, try Yahoo. Check out the Yahoo Calendar Share link, which allows your whole family to modify and view a single calendar. Once you pick a calendar program, just make sure everyone knows how to enter new items or has the username and password if it's web-based.