Google Calendar Sync

http://www.google.com/support/calendar/bin/answer.py?answer=89955

Google Calendar Sync: Getting Started
Google Calendar Sync allows you to sync events between Google Calendar and Microsoft Outlook Calendar. You'll be able to determine the direction of information flow, as well as the sync frequency. Staying on top of your Google Calendar and Microsoft Outlook Calendar events has never been easier!

Keep in mind that it's not possible to sync events on secondary calendars at this time. Google Calendar Sync will only sync events from your primary Google Calendar and your default Microsoft Outlook calendar.

Get started
To begin syncing, follow the steps below:

To download Google Calendar Sync, visit http://dl.google.com/googlecalendarsync/GoogleCalendarSync_Installer.exe
Once a dialog box appears, click "Save File." The download should open automatically. If it doesn't, manually open the download from your browser's download window.
Click "OK" to confirm that you're aware this is an executable file.
Read through the Google Calendar Sync Terms of Service, and click "I Agree."
Continue to follow through the Installation Options and click "Install" to finish the set-up process.