<< What will be changing? Today, Google Apps accounts can access, Gmail, Calendar, Docs Sites and a limited set of other services. Later this year we’ll address this technical limitation once and for all, and give users the convenience of accessing any service allowed by their administrator from a single account affiliated with their organization.

Which applications will be available to Google Apps customers? With a few possible exceptions, Google Apps customers will be able to use all Google services. We will continue to update this area of the Help Center as more information becomes available about this.

When will this change happen? We intend to have all Standard, Premier and Education Edition customers moved to the new infrastructure that enables this change in the fall, and customers who would like more control over the timing of this change will be able to voluntarily make the switch during the summer. >>

http://www.google.com/support/a/bin/answer.py?answer=181171