Designed for organizations in which some users use Google Calendar and other users manage their calendars in Microsoft® Exchange, Calendar Interop enables you to sync thefree/busy status of users in both calendar systems.
This enables users in one calendar system to view the availability of users in the other system before scheduling a meeting.
Editions included:
Google Apps for Business
Languages included:
All supported languages
For more information:
http://support.google.com/a/