Google Apps(Applications) for Your Domain

Get your people talking
Google Apps for Your Domain lets you offer private-labeled email, instant messaging and calendar accounts to all of your users, so they can share ideas and work more effectively. These services are all unified by the start page, a unique, dynamic page where your users can preview their inboxes and calendars, browse content and links that you choose, search the web, and further customize the page to their liking. You can also design and publish web pages for your domain.

It's all free* and everything is hosted by Google. No hardware or software required.
You can choose any combination of these Google services
Start page
The start page - A central place for your users to preview their inboxes and calendars, access your essential content, and search the web.
Gmail
Gmail - Offer email to your users with 2 gigabytes of storage per account, search tools to help them find information fast, and instant messaging built right into the browser.
Google Talk
Google Talk - Your users can call or send instant messages to their contacts for free -- anytime, anywhere in the world.
Google Calendar
Google Calendar - Users can organize their schedules and share events, meetings and entire calendars with others.
Google Page Creator
Google Page Creator - Create and publish web pages for your domain quickly and easily with this what-you-see-is-what-you-get page design tool.

Sound interesting?

To sign up, go to http://www.google.com/a/