You can use the group email alias to share calendars, documents, sites, and videos in Google Apps. As you add new people to groups, they'll gain access to resources you previously shared with that group. Let's call them smart groups because they adapt to changes within your organization.
For example, using the alias 'firstname.lastname@example.org' you can give access to anyone who is a part of the 'faculty' group in your school Apps domain. Any new faculty members you add later on will automatically gain access to shared items. Likewise, any faculty members removed from the group will no longer have access to the shared items.
In Google Calendar, you can share a calendar with a group by
navigating to 'Share this calendar', and then entering a group's email
address where you normally enter an individual's. The calendar will be
shared with everyone in the group, and will automatically adjust to any
membership changes over time.
In Google Docs,
groups can be given permission to edit or view individual documents,
spreadsheets, presentations, or files. Use the 'Share' button and
invite the group email address to be the owner, collaborator, or viewer
of the document.
In Google Sites,
you can share a site with a group in the same way. When you go to 'More
Actions' > 'Share this site', choose whether you want everyone in
the group to be an owner, collaborator, or viewer. Enter in the group
email address, select the appropriate sharing level, and the site will
be shared with everyone in the group. The site will automatically
detect group membership changes - if you remove one member from the
group, they will no longer be able to view the site.
In Google Video, you can make a video available to a group as well by adding a group to the collaborator or viewer list.