Google has announced Google Apps for Government, featuring the same applications in other versions but with a higher level of security. Cost is $50 per user per year.
Google says meets the requirements set forth by the Federal Information Security Management Act. This includes segregated data centers, which Google says goes beyond FISMA regulations, and will keep government e-mail and calendar event data within U.S. borders.
Google Apps for Government homepage:
http://www.google.com/apps/intl/en/government/#utm_campaign=govapps&utm_source=ogb-appsforgov-0710&utm_medium=blog