It was long time ago I have registered to use the Gmail Hosted beta service. last week I received an email from Google team which announced the availability of the beta service.
Here you can see some screenshots from the administration panel and it's user interface.
The best part is Google Calendar in my opinion which you can use across your small office/team.
If you want more information about this service, I suggest to read it's FAQ page here : Gmail for your domain FAQ
This special beta test lets you give Gmail, Google's webmail service, to every user at your domain. Gmail for your domain is hosted by Google, so there's no hardware or software for you to install or maintain.
Gmail – 2 gigabytes of storage and search tools that help your users find information fast. Instant messaging from right inside their accounts.
Google Talk – Users can call or send instant messages to their contacts for free – anytime, anywhere in the world.
Google Calendar – Users can organize their schedules and share events and calendars with others.
Control Panel – Easily manage user accounts, aliases, mailing lists, and chat settings.