The critical piece of missing information was how to build the CalDAV server address for the all the calendars you have set up in Google Apps. It is important to remember that all of the sharing and setting of permissions for calendars is controlled by the web interface. You will need to go into the settings panel for each calendar to find the Calendar ID for each calendar you wish to add.
The CalDAV address for your primary calendar is always https://www.google.com/calendar/dav/YOUREMAIL@DOMAIN.COM/user where your Google Apps account replaces YOUREMAIL@DOMAIN.COM. On the settings page of each of your calendars there is a section labeled Calendar Adress. To the right of the XML ICAL and HTML buttons you will see the Calendar ID. The CalDAV server address you will use when configuring iCal to sync with the Google Apps servers is https://www.google.com/calendar/dav/{CalendarID}/user.
It would be nice if Outlook could consume CalDAV natively like iCal which would make working with multiple Google Calendars as easy as this in Windows.
Detailed step-by-step instructions are in the full version of this blog post below.
