If you use the Google calendar, you can connect it to Outlook.

Using Outlook 2007, the calendar will be listed under Other calendars. Changes made to the Google calendar will be updated automatically, approximately hourly. At this time it's a one-way sync: you cannot make changes in Outlook and update the calendar at Google.
In older versions of Outlook, download the ics file and use File/Import Export to import the events to the default Calendar folder. Events are not updated automatically, you'll need to download the ics file and import it again (which will result in duplicates of existing items).

1. Click the manage calendars link on the Google calendar page then Shared: edit settings, then the calendar Details tab.
2. Outlook 2007: Right click on the private ical button and copy the link. Paste that into the Internet calendar, New setup dialog at Tools, Account Settings.
   Older versions: click the ical link and again on the URL that comes up. Download the file and import into your calendar. If you have Outlook 2007 and download it, you'll have the option of opening it as a new calendar or importing it, however, using this method creates a static calendar in Outlook 2007.

If you use Vista, you can add it your Vista Calendar using steps similar to those used for Outlook 2007.