Google Apps including, email service (Gmail), Google Docs, Calendar, Gtalk, free with hosting package.

Google Apps brings together essential services to help you communicate and collaborate more effectively. These services are powerful, easy to set up, require no maintenance, and you can get them for free. Everything is unified by the Start Page, a central place for your users to preview their inboxes and calendars, access your essential content, and search the web. Administrators can choose to deploy a mix of the communication and collaboration products listed below.

I found this at Idotz. I use Google Aps Mail, Gmail for one of my domain. Its same like using Gmail with all the features.