Google Apps for domains is Google's private-label version of its Web applications. You get Gmail, Google Calendar, Google Docs, and more. For Gmail, instead of having whatever@gmail.com as your address, you have whatever@yourdomain.com. Also, the calendar, Docs, and other applications are integrated, and can be administered centrally. It's Google's attempt to compete with Microsoft Exchange.

It comes in a free version, or a $50 per user per year Premium version, with tech support and increased email storage quotas.