iCloud works well for sharing your own calendar in the Apple world. But if you have an Android phone, or want to share a calendar on the web, Google Calendars is much more powerful. The Google calender service is the easiest and most flexible free shared calendar service that I’ve found. Here’s how to set it up on a macintosh computer.

1. START A GOOGLE CALENDAR.
Go to google.com, and if you don’t already have one, create a gmail account. (Even if  don’t need to use gmail for email you still need to create a gmail account to sync your calendars using Google.)

Login to your gmail account, and select MORE – CALENDAR to start your own google calendar.

2. PUT YOUR GOOGLE CALNEDAR INTO ICAL
Go into ical and select ical – preferences.

Now select the ‘Accounts’ Tab, then click the + button to add an account.

Now select ‘Google’ under Account type, and then enter your gmail address and password.

That’s it. Press the create button and your gmail calendar will show up in ical. You can edit it, make changes, and it will automatically sync from google to ical.

NOTE: The above method will completely sync your information both ways. Any information edited on one computer will automatically copy across to the others. If you want the sharing to be one way only (for example to share a calendar with a friend but so that they cannot edit it, simply proceed as above on your computer, but then go into gmail, calendar settings, and get the calendar URL.  Copy the URL and in your friends ical select ‘Calendar’ and ‘Subscribe to Calendar’ and paste in the URL. This will allow them to see your calendar but not edit it.

See here for how to sync your Address book.