MAIL: You can setup Google apps to run all of your email addresses connected to your domain. So if your domain name is "stuff.com", then you can have as many email addresses as you would like with that domain. For example: Owner@stuff.com, Joe@stuff.com, Office@stuff.com, or whatever you choose.
CALENDAR: Each person can have their own calendar, but with the sharing options you can bring up the main calendar for your organization and see what everyone is doing at any given time.
DOCUMENTS: This is one of my favorite features. Google Drive through Apps allows for document sharing on any computer or mobile device. We keep up with our customers through Google Drive Apps, no matter where I am I can update a customers information on Drive and the other members of my team can see it immediately. Drive includes documents, spreadsheets, databases, and presentations.
These are the main features we use everyday. In addition to these, there is a video conferencing system, an internal website builder for project management with your team, a management dashboard, and other features. The management dashboard allows your administrator to mange the entire system, adding and removing people, restrictions, privacy, and general settings.
Google Apps has two pricing options, $50 per user per year or you can choose to pay $5 per user per month. The latter option is best if you have people coming and going from your organization, you can add and remove them easily. If you are a 501C3 non-profit then you can apply to use Google Apps for FREE.
See more features HERE.