Gmail, Google Calendar, Google Talk and Contacts

On some Android-powered devices, (for instance the T-Mobile G1) Google applications come pre-installed. Access these apps by tapping their icons. When setting up the phone, make sure to log in using the username and password for your domain, and your content will be automatically synced on the go.

Gmail, Google Calendar and Google Docs in the mobile browser

These apps are also available in a single, streamlined web interface, where you can seamlessly switch between applications. Bookmark http://www.google.com/m/a/example.com from your browser and add a shortcut icon to your homescreen by long-pressing and selecting the 'shortcut' then 'bookmark' options. But don't forget, you'll have to replace "example.com" with your actual domain name.